[1] She participated in the Battle of Miyako Bay, when three Tokugawa Navy warships were dispatched for a surprise attack against Imperial forces.

For the battle, Eugene Collache, a French navy officer, was put in command of the Kaiten No.2, on which were sailing 40 seamen and 30 samurai.

The ships encountered bad weather, in which the Kaiten No.2 suffered engine trouble, and the Banryu was separated.

To create surprise, the Kaiten No.1 planned to enter Miyako harbour under an American flag as a ruse de guerre.

The Kaiten No.1 approached the enemy ships and raised the Tokugawa banner seconds before boarding the French-built Kōtetsu, of the opposing Imperial navy (the first Japanese ironclad).