Toumei Ningen no Tsukurikata

Saitou Shinji is an Ordinary High-School Student living a peaceful life on a peaceful island… way too peaceful for his tastes. The only two things he enjoys on the island are the pranks he plays and the time spent with his Childhood Friend Kana, a cheerful girl who loves taking photos and understands Shinji better than anyone.

However, when he runs away after an incident where he got angry and punched several classmates in the face, he receives a mysterious e-mail on his cellphone: "If you answer this e-mail, you too can become an invisible man!" He answers it while laughing it off… but the day after, everyone has inexplicably forgotten about the incident, and a mysterious white-haired girl appears before Shinji, calling herself an "invisible woman." He soon realizes that answering this e-mail may take away from him the only thing he holds dear…

(Source MU)