Co by kdyby?

Kujo Rina is a chemistry teacher and the homeroom teacher for the 3rd grade D class at Horai High School. She doesn't have a bond with her students. On the school's graduation day, Kujo Rina is pushed from the 4th floor and falls down. She is able to glimpse a school uniform sleeve on the person that pushed her. At that time, she wonders why she was pushed and that she does not want to die.