Star Gym is the Gym where Isamu Take and Moka Kaname train. It's a gym run by Hyouma Hoshis family. Hoshis father is, during the begining arc, the owner and head trainer. It is the first gym that Isamu Take and Moka kaname train at as well as the gym that they fight out of in the begining arc.
Star gym is a small gym with heavy bags, a speed bag, and a single boxing ring.
Under the gym is also a secret room in wich Hoshis family perform wild, evil experiments on people they have captured (verified by Hyouma hoshis hostile attitude and body language during chapter 55). Includeing Hoshis black market drug running, prostitution and secret murder of his sister and father. It is a representation of human will to survive that eventually fails. It is burned to the ground during chapter 180 during a flameing fist of death, death match between Isamu Take and Hyouma Hoshi.