Секта по бадминтону

The main character is a Japanese private detective working with the police.

One day, a student disappears under mysterious circumstances... and soon, a life-size, realistic doll of her is found in a park.

Who created it, why, and is the missing woman still alive?

The only clue is a private badminton club the victim frequented and where she rented a room. Rumor has it that this club is simply a front. After all, suspicious people dressed as cultists are seen wandering around the club at night...