Pu-erh-like tea called Batabatacha from Toyama Prefecture.

How about BATABATACHA
Batabatacha is a tea that has long been loved by the people in the town of Asahimachi Birudan of Toyama Prefecture. It is a fermented tea quite similar to pu-erh tea.
Early August is the harvesting season for tea leaves used in making batabatacha. Tea leaves are steamed in a pan until the color becomes yellowish-brown. Steaming process stops the function of enzymes. After drying the tea for half-day, it is placed in a wooden box for fermentation. The last step is to take the tea out from the box and fully dry it under the sun.
In this particular region of Toyama Prefecture, batabatacha is served at various events such as a gathering for ancestor's commemoration or when introducing the bride after the wedding ceremony. As a type of 'tea party' held among family, close relatives and friends, the serving of this tea is ceremonial, but casual at the same time. Brewed tea is poured in a tea bowl to be whisked until it creates a foam. People in the town also drink unwhisked batabatacha with their everyday meal.

Vitamin B12
We have not tested batabatacha for vitamin B12 ourselves, but this study claims that the tea contains a significant amount: '456 ± 39 ng per 100 g dry tea leaves and 2.0 ± 0.3 ng per 100 mL of tea drink'. The study conducted testing on rats concluding that 'the vitamin B12 found in the fermented black tea is bioavailable in mammals.'
Source: Hiromi Kittaka-Katsura, Syuhei Ebara, Fumio Watanabe, and Yoshihisa Nakano. 'Characterization of Corrinoid Compounds from a Japanese Black Tea (Batabata-cha) Fermented by Bacteria.' Journal of Agricultural and Food Chemistry. 2004, 52 (4), pp 909–11. (Abstract is available without membership.)

Additional Information
INGREDIENTS
Green tea leaves from Toyama prefecture
Net Weight (per item)
100g (3.52oz)
Vendor's Retail Packaging
Resealable, Bag
Region
Toyama
Supplier Notes
Family operated, Tea Shop
Season
Autumn harvest

STEEPING NOTES
Kettle Brewing
Boil about 2L (8.5 cups, 68 fl oz) of water in a kettle. Put 10 grams (0.35 oz) of tea leaves into the kettle and brew for 10 minutes. Enjoy it hot or cold.