Gen Shiomi, the 56-year-old boss of the Hitotsubashi mob syndicate, must go into hiding to protect his life from potential assassins. He opts to get plastic surgery, only to end up looking like a teenage girl, but he resolves to stay like this until his life is no longer in danger. However, he finds it hard to not be suspicious, but he is saved from being the target of police by a teenage boy named Tatsuya Umemiya. After helping Tatsuya out of some troubles of his own, Gen is forced to enroll into junior high school as "Shiomi Iwao", only to discover that one of his new classmates is Tatsuya.
Shitei Bouryoku Shoujo Shiomi-chan provides examples of:
- And the Adventure Continues: At the end of the series, with all his foes wiped out, Gen goes under the knife to get his old body back. Unfortunately, when he wakes up he learns that his gang is now in a war with the Russian Mob, meaning that he still needs to stay in the body of a girl, with the only thing the surgeon changed being the size of his breasts.
- Artistic License Biology: There is no way a plastic surgery would be able to make a big man look like a little girl, but this is precisely the point. This can be also seen as a parody of some episodes of Black Jack, where borderline/impossible surgeries are done.
- Be Careful What You Wish For: Gen wanted to be unrecognizable. He got his wish.
- Belligerent Sexual Tension: Akane and Tatsuya. Akane has also a more sweet and feminine childhood friend who supports her, a la Asako and Mayuko in Ushio and Tora. However, Tatsuya is no Ushio.
- Berserk Button: Tatsuya's reason for giving away his money.
- Cliffhanger: During the fight with the hitmen.
- Gender Bender: Physically, at least, from Gen Shiomi to Shiomi Iwao.
- Love at First Sight: Tatsuya to Shiomi.
- Luke, I Am Your Father: Definitely avoided in Chp.8. Gen, after he found to have a son: "There's no way I can do that". He is mentally trying to represent the scene, where he is still the schoolgirl with her usual angry look, doing the revelation to a very shocked Ichiro.
- Magic Plastic Surgery: Gen gets turned from an old man to a teenaged girl through a miraculous procedure. The surgeon in question chose this procedure partly because he modeled Shiomi's new body after an idol he's a fan of, but also to ensure that he isn't simply killed off afterwards since he's the only one capable of reversing the procedure.
- Nightmare Fuel Station Attendant: The hitmen appear to be this trope.
- One is a bandaged blind man with a sadistic streak, able to pursue his victims through scent and using butcher's hooks as weapons; then he is fond of speaking about the fear. Another, Kagachi, resembles a sort of snake woman (she is not). They obey a Perpetual Smiler old man.
- It is possible that Kagachi considers the girl Shiomi Iwao in this way.
- Older Than They Look: Shiomi is a 56-year-old man made to look like a female middle schooler.
- Shout-Out: The surgeon, the so-called "hands of God", is Black Jack by Osamu Tezuka. Not only does the guy have his characteristic scarred dark appearance, he is also directly named as Kuro Hazama (at least in a translation). On the other hand, some traits of his personality are slightly different: after his work, he merrily displays some of the same quirks as Takamizawa, the otaku of Midori Days.
- Slasher Smile: Girl Shiomi does it often, in some cases masking it immediately by putting a cute face.
- Took a Level in Badass: Shiomi can still fight after the surgery.
- We Meet Again: At the end of chapter 1.