"I told you I wouldn't forgive you, didn't I?"

Sota Yukimura (Hokuto Matsumura) works in the secondary brand division of the cosmetics company "Nose Cosmetics." He goes on a Ferris wheel date with his boss, Mariko Nose (Sae Okazaki)—whom he has secretly loved for 25 years—and spends a dreamlike time with her... but that happiness is short-lived. His secret is exposed: he had attended the same junior high and high schools as Mariko all along. Upon realizing that Sota had been watching her from nearby for so long, Mariko is unable to hide her bewilderment and leaves him behind to go home... "It's over... my 25-year-long love..." Sota is devastated, believing Mariko now hates him... Meanwhile, the police—led by Detective Taisuke Sakura (Tetsuji Tamayama) of the First Investigation Division, who suspects Sota of murder—uncover the fact that Sota and Mariko attended the same schools and begin to speculate on a motive. They suspect that Sota, harboring an intense obsession with Mariko, may have killed Tsuyoshi Tateiwa (Tomomi Maruyama), a colleague who was vying with Mariko for a position within the company... Furthermore, Taisuke visits the detective agency Tateiwa had hired and obtains crucial documents that hold the key to the events leading up to Tateiwa's murder... Amidst this, Sota—determined to protect Mariko's happiness—grows suspicious regarding the accidental death of Mariko's biological mother, Kyoko, and goes to meet a certain individual... And finally, the true culprit behind Tateiwa's murder is revealed! Just who is the killer...!?