Takeru Watanabe is a mankaka (manga creator) who draws magical girl manga to pay the bills, but his true love is Sumo. He wants nothing more than to graduate from his local amateur sumo organization and become a top pro! Unfortunately, while he's a bit above average in strength, he has trouble packing on the pounds, so he's usually pushed out of the sumo ring pretty quickly if his opponent can get a little inertia going. One day, a "fairy godmother" (the auntie from his favorite chanko place) tells him that she can help, if he swears to help the innocent whenever he sees someone in trouble. She sweetens the deal a bit by offering a special price on meals, if Takeru comes in to eat immediately after subduing 'wrongdoers.'

For a man who sees his thirties just a little over the horizon, it sounds like a great deal! He just didn't quite catch the part where he has to transform...