Fatty, a high school student, was first seen after Josuke followed some of his Harvest's stands during a coin collecting spree in fear of finding a potential enemy stand user. At first Josuke and Okuyasu believed him to be a complete idiot by his strange demonstration of generosity to share the wealth he had just accumulated by Harvest (which he did in order to become their friends), though Josuke insisted on not taking advantage of his naivete, but instead work together with Fatty and then equally share the spoils. Soon Josuke and Okuyasu's plan backfired as Fatty turned on them, insulted at being called an idiot and selfishly not understanding that they deserved the equal share of the money they had all worked for together. This started a wild goose chase after him at which point Fatty revealed that Harvest's advantage relies heavily on his numerous stand parts. Using multiple attacks from Harvest's men combined with dirty tactics, such as having Harvest inject alcohol directly into the blood stream of Josuke and Okuyasu, Fatty proved to be a tough opponent.
After being subdued, Fatty finally admitted that Josuke and Okuyasu were indeed deserving of one third each of the money they had gotten together. They then became friends at school.
(Source: JJBA Wikia)