SKMJ-742 Congratulations on becoming a working adult! A sister and brother, who are moving to Tokyo for work, try taking a family bath together for the first time in 10 years, with only a towel between them! They shouldn't be conscious of each other as members of the opposite sex, but they end up bathing together in a tiny bathtub! The extreme mission makes them aware of each other... and the close brother and sister end up having unprotected sex!

A close brother and sister take on the challenge! A forbidden intimate monitoring project! A man and a woman who were absolutely forbidden from having sex before moving to Tokyo are forced to share a small bathtub for the first time in 10 years. Will they cross the line and have unprotected sex?! The brothers enter the bathtub in their natural state with a large cash prize at stake! The two have grown into mature adult bodies. Theドキドキ (heart-pounding) mixed-sex bathing experience begins!