[2] Although it has a body shaped similar that of other fantailed goldfish, its tail fin opens and spreads flat and wide horizontally with the leading edges flipping under once or even twice.

The Tosakin has been often and mistakenly reported by as a weak fish due to inbreeding, but it is as hardy as most other breeds of fancy, deep-bodied goldfish.

He managed to trade a large bottle of shōchū (焼酎)(Japanese sweet-potato vodka) for the fish, and was able to successfully revive the Tosakins in Kochi.

In 1971 the breed had reached Tokyo, where a small group of avid young enthusiasts painstakingly propagated and popularized the variety.

In order to achieve its connected, fanned-out appearance, the Tosakin has traditionally been kept in shallow, round bowls that allow the tail to fully develop during the fish's first year of life.

The low water level and rounded corners of the enclosure prevent excessive upward and downward movement, allowing the Tosakin's tail to form correctly and achieve the distinctive spread-out fan style.