When he was a child, Murakami was friends with a girl he called Kuroneko. One day, while trying to prove the existence of aliens to Murakami, she is killed in an accident that he barely survives.

Murakami Ryota's best friend, Kuroneko, died in an accident trying to prove aliens existed when they were kids. Now, a girl who looks just like her transfers into his high school. When confronted ...