Eons ago, in ancient Japan, two warring factions were battling across the atchipelago: The Sumotoyas, and the Hishimotas. The war had been ravaging the land for an eternity, locked in an unbeatable stalemate. Both sides were looking for an advantage, and one found a way. An ancient sorcerer of the Hishimota empire whose name was forgotten to time stepped forward and placed a curse on the Sumotoyas. It was designed in such a way that whenever a Sumotoya took a victory over anyone, they would get big and heavy, making them weaker and slower, which would give the Hishimotas the upper hand. However, something went wrong with the curse. When the first Sumotoya warrior cut down a Hishimota, they did swell big and fat, but instead of becoming weak, they were given ungodly strength. The Sumotoyas overtook their enemies, which made them more powerful every time they killed a warrior. The sorcerer was banished for his incompetence, and the Hishimota Dynasty fell to the powers of the Sumotoyas.
Eons later, the curse was still present in society, mainly secluded in Japan and Korea. Countless variations on the curse make it wildly different than it once was. The rough rules were, whenever you achieved any victory over another, you'd slowly swell fatter for the rest of your life. The speed of the curse would double every time the cursed was victorious again. The curse was spread from bodily contact, but only very rarely. And the curse used to be isolated in Japan, but a huge migration caused it to spread to the Americas, specifically the USA.
You have been cursed by a passerby on the sidewalk. Who are you, and how does your life change because of this drastic curse?