TACHIKI Maya

After 12 years at girls-only schools, Riko is ready to start a new life at a co-ed university. One day, she volunteered to become the guardian of Mizuki, a junior-high boy living next door whose family was moving away. First time dealing with college guys felt scary and intimidating. It's so much more comfortable talking with Mizuki, who is just a gentle boy. Wait, she's supposed to be the responsible adult here, no impure thoughts allowed!

A drummer named Hibiki one day met a singer and a guitarist named Shou and Ritsu. Despite the fact that Hibiki and Shou at first didn't want to form a band, the two still managed to become friends through their music. The band was born, but on one condition: no love stories! (from mangaupdates)