Manami is introduced to her best friend Aoi by her younger sister Anzu. One day, while her sister is in the kitchen, Aoi sneaks around Manami's breasts and gives her a French kiss. When she ends up staying over at her house, she sneaks into Manami's room, soaks her nipples with saliva until her tank top gets damp, and licks her sweaty crotch. The two make love with each other until dawn, fingering each other, and from that day on, they sneak around, sometimes boldly, trying not to get caught by their sister, and cover her young skin with love juices with cunnilingus and tribadism.