Police officer Haruhi Mabuchi is monitoring suspended detective Suzunosuke Shikahama when Ruka asks him to solve a case. Haruhi turns to Suzunosuke for help, but the case gets stalled until Public Safety Officer Sesuna Tsumiki gets involved.

Suzunosuke goes on an odd rant about love after Haruhi shocks him by announcing his wedding. Ruka worries about Detective Hattori when she confines herself in the precinct for a murder investigation, and takes the case to Suzunosuke.

Haruhi realises that Suzunosuke's recent strange behaviour is due to his crush on Sesuna, who is caught up questioning her own skills as a police officer. Suzunosuke tries to win her heart by working with Haruhi and Ruka to help her solve her case.

After a series of attacks on the public, the mysterious World Hero Association declares it will continue to punish anyone who breaks society's rules. Suzunosuke reluctantly lets go of his suspicion that his neighbour Morizono is a serial killer.

Morizono locks Suzunosuke in a secret room in his basement and they eventually learn about each other's pasts. Sesuna is worried about Haruhi's decision to investigate his brother's death.

Suzunosuke is baffled when he runs into Sesuna in Tokyo and she acts like a completely different person. After learning that she had been missing for nearly a day, he lets her stay as she opens up about her past with a woman named Risa.