After returning home after two years, the tall sister Ami (Ayanase Tsuki) treats her younger brother Fujita and Yoichiro like children despite their short stature compared to hers at 173 cm. Despite being treated like kids, both brothers have always had a huge crush on their older sister and would secretly masturbate while wearing her underwear. One night when they all slept together spooning by the river, Fujita's long-simmering desires finally exploded, leading to a passionate threesome where he and Yoichiro take turns pleasuring their beloved big sis! Note that the recorded contents may vary depending on the distribution method.