Tantei wa Sauna de Nazo o Totonoeru

Detective Ryuji Mizuta's father-in-law, Ryutaro Oguro, wants to become a detective. Ryuji tells him about a case he has already solved as a trial, but his guesses are always off the mark. But when Ryutaro took him to a sauna in a hot spring resort, he said, "I have solved all the mysteries."