After Frisk goes missing, Caitlin, Frisk's twin sister goes looking for her in the the last place she saw her. MT Ebott, the mountain of dark legends, she finds a necklace that belonged to Frisk on the ground. Just like Frisk, Caitlin tripped and fell into the Underground. Caitlin finds things she never knew existed.

Y/N is secretly All Mights daughter and gets into UA Hight by Recommendation. Her mother passed away when she was little so she barely remember anything about her. Y/N is very unique with her quirk as she has three. She inherited two from her mother; Explosions and Teleportation. The third she didn't get from her mother or father but inherited it herself; she has the ability to giver herself any quirk she wants. She is a rebellious teen, what happens when she meets Katsuki Bakugo?