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!