A certain son's story. For home renovations, Yasuhiro Sawamura and his mother Reiko Sawamura are staying at the house of their aunt Sorami Hagakawa, who is actually Reiko's younger sister. They are borrowing a room in the family home of Tatsuo Hagakawa, their cousin who lives alone while attending university in Tokyo. However, it's still not their own home, so they can't help but feel uneasy. Reiko also seems to be conscious of the fact that she is living in someone else's house, and never stops working hard on household chores… And then, while watching Reiko like this, Yasuhiro finally noticed something… His mother's bra was floating…
