One day, a college student named Miyu learns from her mother that she has a half-brother. When Miyu was young, her father, who had divorced her mother, remarried another woman, but she disappeared after giving birth. Then, her father recently passed away, leaving no relatives to take care of him. Miyu's mother wants to take him in and raise him. Thus, her half-brother Yuuya comes to live with them, but since he was raised in an all-male household, he struggles to adapt to the new environment. Seeing this, Miyu tries to cheer him up by gently letting him touch her breasts…
