Ichiha

Ichiha and Seiko are friends. Ichiha being more experienced tries to incentivize Seiko's sexual discoveries through gifts and situations, including, even, matching her own uncle/boyfriend to Seiko's first real sexual intercourse.

Note: volume 1 is focused on "Ichiha" and volume 2 on "Seiko", hence their titles: "壱葉" and "聖子"