Believing that a demon haunts Tokyo's streets, Meiko Inoue, a graduate aged 23, feels unsatisfied with her monotonous life and yearns for the excitement of her youth. This compels her to ponder what she truly desires. Shockingly, when she suggests quitting her job to her boyfriend, Naruo Taneda, he promptly agrees.
Encouraged by his vague support, Meiko leaves her old life behind and begins afresh, accompanied by Taneda. Together, they revisit their college dreams and resurrect Taneda's former band, Rotti. However, just as they stand alongside their bandmates, an unexpected event hinders their plan, shattering their expectations.
Solanin explores the personal experiences of young adults in their twenties, often overlooked by society, as they face challenges in love, loss, and grief.