The Naruse and Iizuka families live next door to each other in an apartment building and have built a close relationship over the years as neighbors. One day, the young and beautiful Kokoro marries into the Naruse family. Iizuka, who has known the Naruse family since childhood, is happy about the marriage of the son as if it were his own, but the lively moans of the couple leaking from the walls in the middle of the night gradually take away Iizuka's reason. Then, thinking that he would like to make Kokoro his own, Iizuka invites her to his house and gives her tea laced with sleeping pills...