If you don't mind "cheating", you can use the debug tool (in the key items, named "travel sphere"). Go north until you reach the wall, and interact with the third mirror from the right, you should get the option to change your breast size.
This happens because you have the "titty lover" trait, if you are wondering why you can't change your size normally.
Jin's path isn't finished yet, so you don't get any more scenes at the moment, but I'll add something for him eventually.