[Jikken B-tou] Nee-chan wa Otouto no Are ni Muchuu na You desu. [SDTLs]

A young boy plays outside a traditional home before slipping into the bath to surprise his older sister. As they share a much more intimate encounter in the water, the tension between their familial bond and newfound physical desires reaches a boiling point. What starts as a playful bath-time interaction quickly escalates into a sensory experience where every touch and every sound heightens the thrill of their secret connection.