A high-stakes baseball-knuckle battle takes place between siblings! The older sister is Manasan, 23, working as a shop clerk. The younger brother is Masashikun, 22, and still a virgin. Initially, they justified participating with excuses like "It's fine since we're family" and "There's no way he'll get 100% erect," but now that both have matured, those assumptions no longer hold. The game progresses far beyond expectations—soon, the brother is fully erect, and his arousal intensifies further. Surprisingly, the sister also becomes increasingly turned on despite her shyness, leading to full-on incestuous sex. The brother loses his virginity, and their sibling bond deepens in a sexual way, though questions remain about how this will affect their family dynamics going forward. Originally planned as a variety-style project, this may now continue as a documentary following the evolving relationship between these siblings.