hm~ for one thing it contains incest. Just as a warning, I thought I should say it first then get into the details.
Summary taken from anime news network;
Kayano's dad died several years ago. Her mom is dating and tells Kayano she is thinking of marrying a divorced man who has a son, and Kayano is happy for her. It turns out that this man is her school principal, and his son, Takeru, is a major troublemaker who turns Kayano's life upside down.
if that summary doesnt really make sense then tell me and I'll come up with a better one.

Later.