Megumi Sakura

A teacher and the adviser of the School-Live club who is commonly ignored yet loved by all the girls.

At the beginning of the story, she is dead and all of her appearances are a part of Yuki's delusions, functioning as a sort of ego that keeps her delusions in check.

It is eventually revealed that she turned into a zombie who's dwelling around in the basement, unable to get out. Zombie Megu-Nee is eventually killed by Miki.

In Otayori:

Megumi appears for one last time to Yuki, encouraging her to be a good teacher in her own right.