Associate Professor Akira Takatsuki's Conjecture, Vol. 4 (light novel)

It’s spring, and Naoki is now a second-year college student.As usual, he’s working as Professor Takatsuki’s assistant.One day, Takatsuki receives a request from a woman working in an architectural firm.What’s the truth behind the creepy things happening in the office related to the number four?In June, a weekly magazine publishes an article about the appearance of a mermaid, causing quite the stir.The fervor about mermaids heats up even in Takatsuki’s lecture.On such a day, a dapper British gentleman wanders onto campus—and he’s Takatsuki’s uncle?!Unexpectedly, the man tells Naoki about Takatski’s sorrowful past.Then on a day off, they go investigate the area where the mermaid appeared.There, they meet a boy who tells them that his mother turned into a mermaid.