Based upon the novel of the same name by prolific author Jiro Akagawa, Sailor Suit and Machine Gun tells the story of Hoshi Izumi - Koizumi to her friends - (Hiroko Yakushimaru) - a young schoolgirl whose father has recently passed away. Soon after the death of Hoshi Takashi she receives a letter from him, stating that he’d like his mistress Mayumi (Yuki Kazamatsuri) to stay and befriend her. However, that’s not the end of her troubles. It just so happens that her father was the boss of the Medaka gang and that she’s the 4th Gen successor. But the gang isn’t exactly hot right now as there are only four members: Sakuma (Tsunehiko Watase), Masa (Masaaki Daimon), Aki (Toshiya Sakai) and Hiko (Shinpei Hayashiya). Also they’re in the midst of a turf war with the forty-strong Matsunoki gang who are also affiliated with the Hamaguchi gang. With Koizumi thrown in the deep end it’s up to Sakuma and company to teach her a little Yakuza etiquette, but there’s no time to waste as battles of honour grow fiercer and the arrival of Mayumi sparks a hunt for missing heroine, with a detective named Kuroki (Akira Emoto) hot on the trail.