Tsuneo Shoji has finally reached retirement age, but his wife feels sick when she sits in the passenger seat of the car due to her husband's illness, and his daughter says, "Husband's disease!"
Mio Meguro (Fuka Koshiba) continues her dream of becoming a writer, while living with yokai (folklore monsters) in a share house. She struggles in her job in the editorial department of a publishing company. She proposes plans at her company, but her plans are rejected. A popular AI dating app has become popular, but Mio Meguro isn't interested because of her work. One day, Mio Meguro meets genius mathematician AITO (Ayumu Mochizuki), who was raised in England. She falls in love with him, but her love causes problems for the share house and yokai.
Saya Toma is a female detective with an IQ of 201. Takeru Sebumi is a career detective with a distinguished background. They work on cases by postulating the "SPEC" of the unknown criminals and then deduce the criminal's unknown "SPEC" to make arrests. A mystery occurs when bodies are found on a cruiser in the ocean. Saya Toma and Ryo Kase of the Tokyo Metropolitan Police Department are brought in to solve the case.
After the events of the series, Shibata has lost her memories and is reassigned. Meanwhile, a strange case regarding a cursed tree that kills whoever's name is written on its trunk surfaces among mysterious deaths. Following different leads, Shibata and the Unsolved Cases unit will meet again as they investigate. Asakura, it seems, is also plotting behind the scenes...
