Himiko has had enough of Kokichi's pranks and shenanigans, enough to finally stop saying that she's tired and actually cast a spell on him. She told him that he'd get fatter with every lie he spoke, which obviously didn't mean much to Kokichi. He had seen her "magic", there was no way anything would happen from this, would it?

Commission from a very like-minded anon, who saw the truly tragic lack of Kokichi Ouma weight gain fics in the world and boldly came to me with a story idea to solve the problem. Truly, a visionary of their time. The world needs more fat Kokichi and I am happy to help with that.