Shinno

Shinno is an aspiring guitarist. He is a version of Shinnosuke Kanomura (金室 慎之介; himself) from 13 years in the past.

Shinno has traveled back in time 13 years ago to when he was 17 and meets his ex-girlfriend Akane Aioi's little sister, Aoi Aioi.

Shinnosuke and Akane Aioi were supposed to move in together after graduating high school, but after the death of her parents, she decided not to.

(Source: Her Blue Sky Wiki)