My Sister's Boyfriend adds Taisuke Niihara to cast

Shochiku has added Taisuke Niihara to the cast of My Sister's Boyfriend, the live-action adaptation of Amu Meguro's manga. The announcement was published by Anime News Network on 6 October 2026, citing the film's official website and Comic Natalie.

Niihara will play Amamiya, a new assistant producer at the television station where Momo Sanae works. He joins Masaki Hashimoto as Midori Yukishiro, Runa Nakajima as Sui Sanae, Rinka Kumada as Momo and Reo Matsumoto as Ayame Mizukawa.

Mahito Kimura is directing from a script by Nami Kikkawa. Shochiku is credited with planning and production oversight, as well as distribution. The film is scheduled to open in Japan on 4 December 2026; no wider release has been announced in the sources checked.

Our opinion

This is a modest but useful casting update because Niihara's role adds another link to the film's television-station setting without pretending that one supporting announcement changes the shape of the adaptation. The December date gives Japanese audiences a clear appointment, while international viewers still need to wait for confirmed distribution details.