In the fictional Tokyo suburb of Mahoro, Keisuke Tada works as a "benriya" - a general problem solver for hire.

One day in January, former classmate Haruhiko Gyoten appears unannounced. Back in their schooldays Gyoten was a quiet person who rarely talked. Now, Gyoten won't stop talking. Both men are over 30 years old and divorced. Without giving an explanation, Gyoten suddenly asks to spend the night at Tada's home. Tada turns down Gyoten, but Gyoten is persistent and Tada finally relents and allows him to sleep over for one night. What Tada is unaware of is that Gyoten plans to stay for more than one night. Eventually, Tada accepts Gyoten as his assistant and they become involved in various cases involving an assortment of people from different walks of life.