Classmate, Kamimura Yuuka wa Kou Itta.

Also known as: クラスメート、上村ユウカはこう言った。, 클래스메이트, 카미무라 유우카는 이렇게 말했다

by Tsutsushi Sakurai, Masaki Kawakami

Shirasaki is incredibly bored by his unchanging daily school life and he ends up falling in with his weird classmate Kamimura Yuuka, who rants about changing the world to his uninterested classmates. However, when she reveals the truth about the nature of their world to him, everything will quickly become stranger than he would ever have expected! (Source: MangaHelpers)