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

Haruhi notices 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.

Suzunosuke drops his suspicions about Morizono being a serial killer as police investigate the World Hero Association's vigilante actions. However, his doubts resurface when he sees Morizono with multiple women who seem to be his wives.

Morizono locks Suzunosuke in a secret room in his own basement and the men learn the truth about each other's pasts; Haruhi's decision to investigate his brother's death worries Sesuna as she believes her other personality may be involved.

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.