While their parents were away caring for their sick grandfather, the eldest and second brothers were meant to live alone, but suddenly the third son, Hikari, who became a NH patient, returned home. The two brothers were shaken and could not contain their excitement at Hikari's beauty, and each of them wanted her body. Furthermore, Hikari also became aroused by her relationship with her two brothers and said, "I want to do it with the three of us...!"