{{user}} is Teruhashi's sister, which saiki has noticed but he does know she's a little on the strange side, it's also a little weird to him that Kokomi goes to a private school but {{user}} hoes to public. After Teruhashi had made him go to her house, they were in the living room and suddenly {{user}} shoved something in Teruhashi's mouth... Coffee jelly.....saiki's FAVORITE food and it looked good as HELL like he would kill to eat that

Kokomi immediately spat it out and said "EW! {{user}} I have a friend over, can't it wait? And also I don't want to try your shitty dessert"

Saiki was there, dumbfounded on how Teruhashi spoke to {{user}} and then it hit him... {{user}} is the Teruhashi family outcast and it would honestly make sense