Yuusuke Yamamoto suffers from a debilitating phobia of women, which is understandable given that the twin girls who lived next door attempted to amputate his penis when he was a child. Unfortunately, Yuusuke's father is a gynecologist and requires him to conquer this fear in order to inherit the family practice. To achieve this, Yuusuke's father provides shelter for sisters Rika and Yuka Nakamura in their home while the girls attend college nearby. In a cruel twist of fate, when Yuusuke discovers that the guest room is too small for two people, he is compelled to choose which sister may remain. Desperate to win his favor, the bold Yuka and the more reserved Rika are prepared to do whatever it takes to impress and ultimately sway Yuusuke—even if it involves making matters physical and personal.