In the quiet of their shared home, Miku Nakano, the eldest quintuplet, finds herself drawn to her younger sister, Ichika's, secret stash of explicit magazines. As she flips through the pages, her curiosity turns to arousal, her hand instinctively wandering to her panties. Meanwhile, Nino, the second eldest, catches Itsuki, the youngest brother, masturbating in the bathroom. Instead of shaming him, she joins him, their mutual desire too strong to resist. Their shared pleasure echoes through the house, drawing the attention of the other siblings, who soon find themselves unable to resist their own carnal desires.