Yatsumi was originally an assassin that worked in Morning Shadows as a top executive to Caramella Dawn.

After a mission gone wrong, she encountered the Whitebeard pirates (whom of which are already friends with Dawn) and after spending a few months with them, she decides to leave the life of an assassin behind to become a pirate under Whitebeard.

Yatsumi joins 3 months before meeting Ace in the official story.