Yuri Yuri Panic: An Extremely Precious Affair has Begun!

The following content is intended for mature audiences and may contain sexual themes, gore, violence and/or strong language. Discretion is advised.
The most beautiful girl in my class proposes to me, a loner?! On her first day at school, Akari, a plain high school girl, suddenly receives a marriage registration form from the conspicuous Kiyozumi Runa…?