Yumi Shirakawa is the first character that can be recruited in the game. She is a classmate that the player meets right after they leave the classroom, once Karukozaka High is transported to the Expanse. Should the player accept her, they will be locked onto her path and will go through the worlds of the Expanse, eventually defeating Hazama in his Emperor form without learning of his past. She seems to care about her school, wishing to save everyone inside it. Her path, up until the first battle with Hazama, is identical to Reiko's.
Yumi is the first character that lends their help to the player. Unlike if..., her recruitment is not optional. When she joins the player, she talks to Tamaki Uchida, and is needed to recruit Charlie and Reiko Akanezawa into the party. She is also needed to defeat Beelzebub and "The Emperor".
Yumi is one of the two survivors of the incident at Karukozaka. She's transferred to another school and appears to be trying to move on with her life when Ambassador Thorman's forces attempt to abduct her. She appears to have strong magical powers that resonate with the sealing stone of Amatsugami.