The story begins when Uta Naruse, a primary school student, meets Wao, a high school graduate studying for the entrance examination of a music conservatory. They pursue their ideal music together and inhabit a world of perfect pitch.

From Megchan's Scanlations:

In a small town in Tokyo, the PTA argues about teaching sex ed in elementary school, but what nobody knows is that eleven-year-old Haruna is already pregnant. When she decides not to tell any adults, it's up to her classmates to help her through this ordeal.