Hakuoki Yuugiroku

Chizuru accidentally overhears a secret Shinsengumi meeting and is asked by Hijikata to report anything suspicious. She hears Itou panicking over a lost item he cannot let fall into the wrong hands. When she finds the box and opens it, something goes wrong — every member of the Shinsengumi suddenly shrinks into chibi form. Getting everyone back to normal means clearing a series of mini-games. The captains are no less intimidating at reduced size.