"I'll die with you, I promise." Yoshino is a second-year working adult who is exhausted from her daily life and work. One of the worst days of her life, Yoshino gets drunk and wakes up the next morning to find a mysterious boy named Hana-kun sleeping next to her. Yoshino ends up living with Hana-kun for a limited time, and surprisingly begins to feel comfortable living with Hana-kun. Meanwhile, due to a certain incident, Hana-kun becomes obsessed with her for some reason...