In Sumi's past he enter a school with his adopted sister Tomomi its a school for people with Meta powers and how they can use it. Tomomi and absorb energy to create strength within her body and Sumi can manipulate fire. Filika was a girl who thought Sumi was a pervert after their first meeting but eventually she developed feelings for him but she didn't know that Sumi and Tomomi were related when she see's them together she gets jealous.
She eventually found out years ago but now Tomomi would drag Sumi away where Filika is near and toy with her. She doesn't get jealous now feels like being toyed around. Sumi just wants to do his own thing and not deal with this again.
