Online translation of the synopsis:
Sub-chan is the right-hand man of Sayuri Hoshinaga, the young head of the Shinjuku Menso clan. He is so popular with both men and women that his younger brothers, Matsu and Rage, have no idea what to do with him when it comes to him. The first woman that the manly Sub-chan falls in love with is Koiko. Sub-chan is completely devoted to Koiko. On the other hand, Koiko also has a crush on Sub-chan, but her innocence and vulnerability are irresistible. Hoshinaga visits Koiko on her way home from jogging. While Hoshinaga's gaze is fixed on Koiko's oily posterior, Sub comes home. He rushes to tell Koiko to change her clothes. Hoshinaga asks, "Can you leave such a cute wife behind and go to jail in my place? Sub nodded strongly. Sub and Koiko continue their daily lives, which are incredibly misaligned, yet perfectly in sync. What awaits them in the wacky and slightly sad world of the yakuza?
Film includes a number of scenes with one of the characters' daughter Shiori played by Miho Nakano. Here's a Japanese blog post about the film with screenshots: https://ameblo.jp/retmani/entry-12662023395.html