On the night of their school trip, four girls arrive at a ryokan inn, their excitement at its peak! These four aren't just friends. They're best friends, lesbians, and when they're together, there's a sparkling air of secrecy. When one of them winks and whispers, "Our, our own secret," everyone chuckles. After putting their luggage in the room, they start to relax. While rolling around on the tatami mat, one of them says, "Hey..."