Choi-S's Makoto and M's Riko have matching sexual quirks, making them a close couple. One day, to introduce Riko's best friend Sora to a guy, they plan a hotpot party with four people by inviting Makoto's friend. However, at the last minute, Makoto's friend can't make it, so they reluctantly have the hotpot with just three people. Sora, who was asked to buy alcohol, accidentally witnesses Seiya and Riko having sex. Seiya feels awkward after being seen in the act, while Riko is oblivious. At the hotpot party that was held, Riko had already fallen asleep, and Sora, like a little devil, starts tormenting Seiya's nipples…
