Gero's search for a wife begins with marriage swindler Shirosaki as his advisor. Shirosaki, who claims he can charm any woman in 30 seconds, insists that the best way for Gero to find love is through "helping people." Gero wonders, "How can a hitman help people...?" Shirosaki suggests using an underworld job matching website. One day, a painting theft occurs on a luxury cruise ship that the two are visiting for a rehearsal of their date. There, Gero meets Himekawa Kyoko, a notorious art thief in the underworld.

Gero's new job is to be the bodyguard of Ureshino Shiori, the daughter of the president of a major corporation. Gero infiltrates the university Ureshino attends, posing as a fellow student. Having never attended university before, Gero's eyes light up as he participates in parties and classes, experiencing a life full of firsts. However, his enjoyable campus life is short-lived, as Gero and his companions are ambushed by assassins targeting Ureshino. While they manage to protect Ureshino and continue their student life, Naruko Genya, the "sound user," is steadily making preparations to assassinate Ureshino...