She's been in Kei's class since middle school, and they've stayed in the same year through high school. Souma was actually the one who set up their first meeting on the school rooftop back in their middle school days.
Misora's got a pretty wild ability—she can 'Save' and 'Reset' reality. Basically, whenever she says "Save," everything freezes in place at that exact moment. Later, when she says "Reset," time rewinds and the world goes back to whatever state it was in during that Save. The catch is that the ability wipes everyone's memories, including Misora's own, so nobody remembers what happened between the Save and Reset. It's like those moments just get erased from everyone's minds.
Kei's the only one who doesn't lose his memories when she uses it, though. His ability to retain and recall memories makes him immune to the reset effect, so he's the only one who actually remembers what went down.
Content compiled by AnimeList.moe from publicly available sources.
