However, because your keyword cuts off at "M...", it could also be:
The series consists of 6 episodes , each approximately 18–20 minutes long, totaling about 2 hours of content. Toshoshitsu No Kanojo Seiso Na Kimi Ga Ochiru M...
Details * October 30, 2020 (Japan) * Japan. * Language. Japanese. * Production company. Pink Pineapple. However, because your keyword cuts off at "M
The story primarily revolves around the interaction between a seemingly "perfect" or "pure" (seiso) female lead and the protagonist who enters her quiet world. In Japanese media, the seiso character type is highly revered—representing someone who is modest, well-mannered, and often intellectually inclined. By placing this character in a library, the setting reinforces her isolation and her dedication to a quiet, orderly life. The narrative tension arises when the protagonist begins to chip away at this exterior, leading to a transformation that is both emotional and psychological. Japanese
This likely points to a Japanese light novel, manga, or adult visual novel — perhaps in the “wholesome girlfriend turns lewd” or “corruption” genre. However, since the title is incomplete (ending with “M…”), I cannot produce a faithful academic paper on a specific existing work without more details.
If you were looking for a specific or light novel version (which often serve as the "paper" source for such animations), it was originally based on works by the creator Amam (雨あられ). Toshoshitsu no Kanojo: Seiso na Kimi ga Ochiru made - IMDb