The body of Yasuko, the wife of company president Mizukami Yojiro, is found their home pool. However, a v-shaped wound is found on her forehead and the home seems have been robbed. The suspects are numerous. Yasuko was disliked for trying to ensure her son will be her husband's successor while also harassing their maid, Nana. A strange paper with an infinity mark is found in Yasuko's room.
