Crim technically does attend school online when school starts at first. But due to being in a female avatar, Kou talks quietly to avoid misunderstandings, but everyone assumes Kou is a shy girl anyway. They assume because she’s hospitalized, that she is shy, frail and needs protecting. And we still haven’t gotten to this point.
Crim also needs to start streaming soon at some point as that is one of the key points of her popularity later.
We still haven’t gotten to the whole guilds version of battle royale that is supposed to happen later where multiple guilds are involved, this determines the three demon lords. And establishes the rivalry between Sorleon and Crim.
Once that is over, Crim is finally able to be released from that pod finally so she can go to school. It is only then Kou discovers the gender and racial change from being human boy to what she originally was supposed to be a half-vampire girl. When she attends school the first time in person. She is very popular instantly, the girls in the class already form a protective group around her as the earlier impression isn’t easily gotten rid of yet. Since they still assume she’s a shy fragile girl at the beginning.
I saw in manga raws that show Kou’s mom, Kou looks like her.