Rare, Japanese Goishicha Tea

Rare Japanese Goishicha Tea – Traditional Fermented Tea from Kōchi

Bright sour-plum tang, earthy depth, gentle umami and a smooth, savoury finish. Our Rare Japanese Goishicha is an extraordinary traditional fermented tea from Ōtoyo Town in Kōchi Prefecture, on the island of Shikoku, Japan.

Produced by Nagao Kitamura, this distinctive tea is made from mature Bancha leaves using a remarkable two-stage fermentation method. First, the tea undergoes an aerobic fermentation involving fungi. It is then fermented in an oxygen-restricted environment where lactic-acid bacteria contribute to its characteristic tangy flavour.

The fermented leaves are compressed, cut into small pieces and dried in the sun. Their dark, pebble-like appearance gives Goishicha its name, meaning “Go-stone tea”, after the black and white playing stones used in the traditional Japanese board game Go.

Unlike conventional Japanese green teas such as Sencha or Gyokuro, Goishicha has a complex sour-savoury character. Its aroma brings together warm earth, aged leaves and dried fruit, while the flavour develops through gentle acidity, plum-like fruitiness and mellow umami.

The liquor is clear and bright, with a smooth body and very little astringency. Its distinctive tanginess is a natural result of fermentation rather than an added flavouring.

Traditionally prepared by boiling the tea in water, Goishicha can also be brewed as a longer infusion. Its compact pieces gradually soften and open, releasing a layered, deeply characterful cup.

For adventurous tea drinkers, collectors of rare Japanese teas and enthusiasts of fermented tea traditions, Goishicha offers an experience unlike almost any conventional loose-leaf tea.

Tea Name: Rare Japanese Goishicha Tea
Japanese Name: 碁石茶 (Goishicha)
Tea Category: Japanese Post-Fermented Tea
Origin: Ōtoyo Town, Kōchi Prefecture, Shikoku, Japan
Producer: Nagao Kitamura
Base Tea: Bancha
Harvest Period: Mid-June to July
Harvest Year: Not Specified
Processing: Two-Stage Microbial Fermentation
First Fermentation: Aerobic Fungal Fermentation
Second Fermentation: Anaerobic Lactic-Acid Fermentation
Drying: Sun-Dried
Appearance: Small, Dark, Go-Stone-Like Tea Pieces
Aroma: Earth, Dried Plum and Mature Fermented Notes
Flavour: Tangy Sour Plum, Savoury Umami and Gentle Earthiness
Liquor: Clear and Bright
Mouthfeel: Smooth, with Low Astringency
Traditional Preparation: Approximately 3g / 350ml / Boil 5–7 Minutes
Steeping Method: Approximately 3g / 350ml / 100°C / 4–5 Minutes
Pack Sizes: 50g, 125g and 250g
Caffeine: Naturally Contains Caffeine

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What Makes Japanese Goishicha So Special?

Goishicha is one of Japan's most distinctive regional tea traditions, recognised for its unusual fermentation process, characteristic appearance and tangy savoury flavour.

• Rare Japanese speciality: A traditional regional tea from Ōtoyo, Kōchi Prefecture.
• Named producer: Made by Nagao Kitamura.
• Bancha tea material: Produced from mature leaves harvested in summer.
• Two-stage fermentation: Combines aerobic fungal fermentation with a second lactic-acid fermentation.
• Distinctive Go-stone shape: Dark, compact pieces traditionally cut from fermented tea.
• Natural tanginess: A gentle sour-plum character created through fermentation.
• Savoury umami: A rounded, food-like depth unlike ordinary Japanese green tea.
• Low astringency: Smooth drinking despite its distinctive acidity.
• Traditional boiling: Particularly suited to simmering or boiling in water.
• Unique tea heritage: A fascinating part of Japan's regional fermented-tea culture.

Goishicha is not intended to taste like Sencha, Matcha or a conventional black tea. Its appeal lies in its unusual combination of fermentation-derived acidity, savoury depth and smooth texture.

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What Is Goishicha Tea?

Goishicha (碁石茶) is a traditional Japanese post-fermented tea associated with Ōtoyo Town in Kōchi Prefecture.

It is made from mature tea leaves, commonly described as Bancha, that undergo a distinctive two-stage microbial fermentation process.

The finished tea is compressed, cut into small dark pieces and dried.

Its name comes from the resemblance of these pieces to the stones used in the Japanese board game Go.

Unlike conventional Japanese green teas, Goishicha develops a noticeable tangy or sour quality during fermentation.

Its flavour can include dried plum, gentle earth, savoury umami and subtle fruity sweetness.

The liquor is typically clear and bright rather than thick or heavily tannic.

Our selection comes from Ōtoyo in Kōchi and is produced by Nagao Kitamura, preserving the distinctive character of this regional Japanese tea style.

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From Ōtoyo, Kōchi – A Rare Japanese Tea Tradition

Ōtoyo is a mountainous town in Kōchi Prefecture on the island of Shikoku, Japan.

It is particularly associated with the traditional production of Goishicha, a tea style that differs significantly from the more familiar steamed Japanese green teas.

While Japan is internationally known for Sencha, Gyokuro and Matcha, Goishicha represents a different approach to tea processing.

Instead of focusing on preserving a fresh green-leaf character, the leaves are deliberately fermented through a sequence of microbial stages.

The process creates a tea with a characteristic sour-savoury flavour and a distinctive compressed form.

Goishicha production has been preserved through regional knowledge and traditional techniques.

Our Goishicha is made in Ōtoyo by Nagao Kitamura using mature Bancha leaves harvested from mid-June to July.

Its unusual character makes it an appealing choice for anyone exploring the diversity of Japanese tea beyond conventional green tea.

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Why Is It Called Go-Stone Tea?

The Japanese name Goishicha refers to the appearance of the finished tea.

After fermentation, the tea leaves are compressed and cut into small, dark pieces.

These pieces resemble the stones used in the traditional Japanese board game Go.

The name reflects the tea's distinctive shape rather than its flavour or ingredients.

Each piece is made from fermented tea leaves, not a dissolvable tea extract.

When prepared with hot water, the compressed leaves gradually soften and separate.

There is no need to break the pieces apart before brewing.

Simply allow the tea to open naturally during steeping or boiling.

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How Is Goishicha Made? The Two-Stage Fermentation Process

Goishicha is unusual because it undergoes two distinct microbial fermentation stages.

This process is central to its characteristic flavour.

Stage One – Aerobic Fungal Fermentation

After the tea leaves have been prepared, they undergo a fermentation stage involving microorganisms that grow in the presence of oxygen.

This first stage contributes to the transformation of the leaves before the second fermentation begins.

Stage Two – Anaerobic Lactic-Acid Fermentation

The tea then undergoes a second fermentation in an oxygen-restricted environment.

Lactic-acid bacteria play an important role in this stage, contributing to the tea's distinctive acidity.

The resulting flavour is noticeably different from conventional Japanese green tea.

Rather than fresh grass, seaweed or steamed vegetables, Goishicha offers tangy fruit, savoury depth and earthy fermented notes.

Compression, Cutting and Sun-Drying

After fermentation, the tea is compressed into a compact mass, cut into small pieces and dried in the sun.

This produces the dark, stone-like form that gives Goishicha its name.

Our tea retains this traditional appearance and is best prepared by allowing the pieces to open gradually in hot water.

The fermentation is a controlled part of the tea-making process. It is not the same as tea accidentally becoming damp or spoiled during storage.

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What Does Japanese Goishicha Taste Like?

Goishicha has a flavour profile unlike most conventional Japanese teas.

The aroma is warm and earthy, with hints of dried plum and mature fermented leaves.

On the palate, gentle acidity provides a bright, tangy opening.

This is followed by savoury umami, mellow earthiness and subtle dried-fruit sweetness.

The tea is smooth and relatively low in astringency, making its acidity more noticeable than any drying tannic sensation.

The finish is clean, savoury and lightly fruity.

Characteristic	Description
Dry Tea	Dark, compressed, stone-like pieces
Aroma	Warm earth, dried plum and fermented notes
Opening Flavour	Gentle, bright acidity
Fruit Notes	Sour plum and subtle dried fruit
Savoury Notes	Mellow umami and earthy depth
Liquor	Clear and bright
Body	Smooth and rounded
Astringency	Very low
Finish	Tangy, savoury and gently fruity

Sour plum, dried fruit and earth are natural tasting descriptions, not added ingredients.

For the fullest flavour, traditional boiling is particularly rewarding.

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How to Brew Japanese Goishicha Tea

Goishicha can be steeped like other loose-leaf teas, but traditional boiling is often the most effective way to release its flavour from the compact fermented pieces.

Use approximately 3g of tea per 350ml of water.

Traditional Boiling Method – Recommended

1. Measure approximately 3g of Goishicha, usually one small tea piece.
2. Place the tea in a small saucepan with 350ml of fresh water.
3. Bring the water to a boil.
4. Boil gently for approximately 5–7 minutes.
5. Stir occasionally to help the tea infuse evenly.
6. Strain through a fine mesh strainer or muslin.
7. Serve warm and enjoy the tea's tangy, savoury character.

The tea pieces may float during boiling, so gentle stirring can help the leaves remain in contact with the water.

There is no need to break the compressed pieces apart before preparation.

Allow them to soften and open naturally.

Boiling can release small fragments of fermented leaf, so fine straining is recommended for a clear cup.

Teapot Steeping Method

1. Warm a teapot or heatproof infuser.
2. Add approximately 3g of Goishicha.
3. Pour over 350ml of freshly boiled water at 100°C.
4. Steep for approximately 4–5 minutes.
5. Stir gently if the tea pieces remain floating.
6. Strain completely and serve.
7. Reinfuse with fresh boiling water if desired.

Brewing Method	Tea and Water	Suggested Time
Traditional Boiling	3g / 350ml	Boil 5–7 minutes
Teapot Steeping	3g / 350ml / 100°C	4–5 minutes
Second Infusion	Same tea, fresh boiling water	Adjust to taste

Brewing tip: If the first infusion tastes too light, try the traditional boiling method. The compact pieces often release their full flavour more effectively when gently boiled.

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Why Is Goishicha Naturally Sour?

The tangy character of Goishicha comes from its traditional fermentation process.

During the second fermentation stage, lactic-acid bacteria contribute to the development of acidity.

This gives the tea a flavour that can suggest sour plum, fermented fruit and gentle savoury notes.

The acidity is part of the tea's distinctive character.

It does not mean that vinegar, citrus or sour flavouring has been added.

For drinkers accustomed to Japanese green tea, this may be an unexpected flavour.

Rather than the grassy freshness of Sencha, Goishicha offers a more complex sour-savoury profile with earthy depth and subtle sweetness.

The exact intensity depends on the amount of tea used and the preparation method.

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Goishicha vs Japanese Green Tea

Goishicha and conventional Japanese green tea begin with leaves from the tea plant, but their processing and flavours are very different.

Characteristic	Goishicha	Japanese Green Tea
Processing	Two-stage microbial fermentation	Usually steamed to limit oxidation
Appearance	Dark compressed pieces	Loose leaves or powdered tea
Flavour	Tangy, earthy, savoury and plum-like	Grassy, vegetal, marine or sweet
Water Temperature	100°C	Varies by style, often below boiling
Traditional Preparation	Boiling	Steeping or whisking, depending on style

Choose Goishicha if you want to explore a rare fermented tea with a flavour that differs dramatically from conventional Japanese green tea.

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Goishicha vs Puer and Chinese Hei Cha

Goishicha is sometimes compared with Chinese post-fermented teas because microbial activity plays an important role in their production.

However, it is not a Puer tea.

Puer is associated with Yunnan Province in China and includes raw Sheng and ripe Shu styles.

Chinese Hei Cha is a broader category of regional dark teas, including Liu Bao and Tibetan Zang Cha.

Goishicha is a Japanese regional tea with its own two-stage fermentation tradition.

Its pronounced lactic tang and sour-plum character make it particularly distinctive.

Tea	Origin and Style	Flavour Character
Japanese Goishicha	Ōtoyo, Kōchi – two-stage fermented tea	Sour plum, gentle umami, earthy savouriness
2014 Wild Liu Bao	Guangxi, China – aged dark tea	Forest floor, damp wood and mellow sweetness
2019 Tibetan Zang Cha	Sichuan, China – compressed dark tea	Woody earth, dried fruit and gentle nuts
2017 Aged Shu Puer Brick	Yunnan, China – ripe Puer	Earth, wood, nuts and cocoa-like notes

For a Chinese dark tea with forest-floor notes, explore our 2014 Wild Liu Bao Tea.

For a traditional Sichuan dark tea, discover our 2019 Tibetan Zang Cha Brick.

For a mellow Yunnan ripe Puer, try our 2017 Aged Shu Puer Brick.

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Goishicha and Japan's Fermented Tea Heritage

Japan is best known internationally for green teas, but several regional fermented-tea traditions have also been preserved.

Goishicha is one of the most distinctive examples.

Its history is associated with the mountain communities of Kōchi and the careful preservation of specialised processing knowledge.

Unlike conventional tea processing, Goishicha uses a sequence of microbial fermentation stages to create its unusual flavour.

Similar broad traditions of fermenting tea leaves can be found elsewhere in Asia, including fermented tea-leaf foods in Myanmar and northern Thailand.

These comparisons highlight the diversity of tea culture, although they do not establish a direct historical origin for Goishicha.

Today, Goishicha remains a fascinating expression of regional Japanese tea craftsmanship.

Our selection from Ōtoyo, made by Nagao Kitamura, offers an opportunity to experience this unusual tea style in its traditional compressed form.

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Who Will Enjoy Japanese Goishicha?

Goishicha is particularly suited to adventurous tea drinkers who enjoy exploring unusual processing methods and distinctive flavours.

It is an appealing choice for enthusiasts of fermented foods and drinks who are curious about sour-savoury taste profiles.

Fans of Chinese dark teas may enjoy comparing Goishicha's lactic tang with the earthy and woody character of Liu Bao or ripe Puer.

Its unusual appearance and regional heritage also make it a thoughtful gift for a dedicated tea enthusiast.

Because Goishicha tastes very different from conventional Japanese green tea, we recommend approaching it as a new style rather than expecting familiar Sencha flavours.

For the fullest experience, try the traditional boiling method and taste the tea plain before adding anything.

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Ingredients and Caffeine

100% Japanese fermented tea leaves (Camellia sinensis).

Goishicha is made from Bancha-style mature tea leaves.

Its sour-plum, earthy and savoury notes arise from the tea and its fermentation process, not from added fruit or flavourings.

Goishicha naturally contains caffeine because it is made from the tea plant.

Although lactic-acid bacteria are involved in production, Goishicha should not be treated as a guaranteed source of live probiotics after drying and preparation with boiling water.

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How to Store Japanese Goishicha

Store Goishicha in a clean, dry and odour-free environment away from direct sunlight, excessive heat and moisture.

Keep the tea away from strongly scented products, including spices, perfumes and cleaning materials.

Reseal the packaging carefully after each use.

The tea pieces are compressed and may be brittle, so handle them gently.

For the best expression of their current aroma and flavour, enjoy the tea within its recommended shelf life.

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Frequently Asked Questions

What is Goishicha tea?

Goishicha is a traditional Japanese post-fermented tea from Ōtoyo, Kōchi Prefecture. It is made through two microbial fermentation stages and cut into small dark pieces.

Where does Great Tea's Goishicha come from?

Our Goishicha comes from Ōtoyo Town in Kōchi Prefecture, on the Japanese island of Shikoku.

Who produces this Goishicha?

Our selection is produced by Nagao Kitamura.

Why is it called Go-stone tea?

The finished tea is cut into dark pieces resembling the playing stones used in the Japanese board game Go.

What does Goishicha taste like?

It has a distinctive tangy, sour-plum flavour with earthy depth, gentle savoury umami and subtle dried-fruit sweetness.

Why is Goishicha sour?

Its natural acidity develops during the lactic-acid fermentation stage. The tea does not require added citrus or sour flavouring.

Is Goishicha a Japanese green tea?

No. It is a Japanese post-fermented tea with a different processing method and flavour profile from conventional steamed green tea.

Is Goishicha the same as Puer?

No. Goishicha is a Japanese fermented tea, while Puer is a Chinese tea associated with Yunnan Province.

How do I brew Goishicha?

Use approximately 3g per 350ml of water. Boil gently for 5–7 minutes, or steep in freshly boiled water for 4–5 minutes.

Should I break the tea pieces apart?

No. Allow the compressed pieces to soften and separate naturally during brewing.

Can Goishicha be brewed more than once?

Yes. The tea may be reinfused. Adjust the time according to the strength of the remaining flavour.

Does Goishicha contain probiotics?

Microorganisms are involved in its fermentation, but the finished tea should not be assumed to contain live probiotic cultures, particularly after preparation with boiling water.

Does Goishicha contain caffeine?

Yes. It is made from tea leaves and naturally contains caffeine.

What pack sizes are available?

Choose from 50g, 125g and 250g packs.

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Discover the Rare Fermented Tea of Kōchi, Japan

Our Rare Japanese Goishicha brings together the regional tea heritage of Ōtoyo, a remarkable two-stage fermentation process and a flavour unlike conventional Japanese green tea.

Its distinctive sour-plum tang, earthy depth, savoury umami and smooth finish make it a fascinating tea for curious and experienced drinkers alike.

Produced by Nagao Kitamura and traditionally prepared by boiling, this is a tea to savour slowly and explore for its unusual character.

For another distinctive fermented tea, discover our 2014 Wild Liu Bao.

For a traditional Sichuan dark tea, explore our 2019 Tibetan Zang Cha Brick.

For a rich Yunnan ripe Puer, try our 2017 Aged Shu Puer Brick.

Browse more distinctive teas in our Premium & Rare Loose-Leaf Teas Collection.

Choose your 50g, 125g or 250g pack and experience the extraordinary sour-savoury character of traditional Japanese Goishicha.