Shin was once a student at the educational institution where Professor Sayaka taught. A romantic relationship developed between them while she was his instructor. When the affair came to light, it caused a scandal that forced Sayaka to leave her position and relocate to another college. The aftermath of their relationship continues to reverberate, as Sayaka is later blackmailed over her past involvement with Shin. After transferring, she develops feelings for a different student, placing her relationship with Shin firmly in the past.