Satougashi no Dangan wa Uchinukenai: A Lollypop or A Bullet

Yamada Nagisa, a disinterested teenager, sees no appeal in routine life and intends to enroll in a military academy after graduation. During her final year of middle school, a peculiar new student named Mokuzu Umino joins her class, claiming to be a mermaid. Umino constantly seeks out Nagisa, causing her irritation and discomfort. Initially, Nagisa tries to distance herself, but she starts noticing signs of Umino's suffering.