Jonouchi Hideyasu is a key character in the series Kamen Rider Gaim, part of the larger Kamen Rider franchise. Initially portrayed as a comedic, somewhat underdog figure, he transforms into Kamen Rider Gridon using the Donguri (Acorn) Lockseed. Over time, Jonouchi matures and develops a sense of justice, becoming more confident and reliable. He often acts as comic relief but also showcases moments of bravery and loyalty, playing an important supporting role throughout the series.