Sex Detective Nana: The Phantom of the Sauna is a 2021 film from Okura Pictures, directed by Yokoyama Shōichi.
Kimito Ayumi stars as Nana, a sex detective whose deductive abilities kick in when she orgasms. There's a scene in which she whips out a vibrator in a lift and starts masturbating, the clues then falling into place. To be honest, it sounds a bit like a concept by video game creator Swery65.
In Tōkyō's bustling business district, Shinbashi, women have been mysteriously going missing, and its up to Nana to investigate. Her partner, Hatenashi, is busy hooking up with US agent Kasumi (June Lovejoy), so she instead teams up with Hachi (Mitsuki Aya). Based out of a Chinese-style massage parlour, they work together to defeat the criminal association, ADAM.
Honestly, the story is a bit all over the place, and the character Kasumi doesn't feel integrated at all. But Nana is very cute in her cheongsam, and the theme song "Imagination Bakuhatsu" is pretty catchy. I also like how they integrated the iconic 1945 C11 292 steam engine at Shinbashi's SL Plaza into the film.
In short, this film is a bit of a mixed bag. It's rather incoherent, but I do like the fun characters and the upbeat atmosphere.
★★★☆☆ 3/5