Mitsu no aware

"Mitsu no aware" is a 2016 Japanese film directed by Akio Suzuki, not Stone, but no such director is mentioned in the provided facts. The film stars Fumi Nikaido as Akako Akai, a shape-shifting goldfish who plays the role of erotic muse for an aging writer, Ren Osugi, whose deceased former student/lover Yuriko Tamura, played by Yoko Maki, helps Akako realize her own desires, activating her agency and frustrating the male fantasy the writer is keen to continue.