You have to continue the school stories to unlock it

Originally posted by Eclisis:

I have boxing style but can't find the gym

the gym will unlock by the time you're about a chunk of the way through the Robotics Club, if I'm not mistaken.

Yeah as already said you just have to play the school stories and unlock it when your focus is at 1 i think? I am not sure on that myself i just played random school stories and unlocked it.