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In the countryside, there exists a custom where, in case the eldest son of a family dies, his widow then remarries the family's second son for the purpose of preserving the family name.
This tradition is called "yome-morai" (bride adoption).

In the Tohoku region, there is a long-established Tsugaru lacquerware shop called "Douguchi" that has been in business for 300 years. Youichi, the eldest son of the family that owns the shop, has suddenly died and so the family's second son Shinji gets recalled from Tokyo.

He faces pressure from his parents, who want him to make children with Miyuki, his brother's widow...

(Source: France Shoin)