: Originally a manga, it was adapted into an ONA (Original Net Animation) by Studio Hokiboshi in Spring 2023.

This title falls under the adult/seinen genre (erotic drama, often with netorare / swinging themes). Reader discretion is advised.

The plot typically follows a married couple—often depicted as comfortable but sexually routine—who agree to swap partners with another couple for a single night. The title’s emphasis on modorenai (cannot return) signals the core thesis: such lifestyle alterations are irreversible. The manga uses this premise to dissect: