Suneo is the fox-faced (inherited from his mother) rich kid who loves to flaunt his material wealth before everyone. He is often seen with Gian, serving as Gian's lackey while they bully Nobita together, though deep down he fears and despises him as much as everyone else. Some of the stories start with Suneo showing off some new video game or toy which evokes Nobita's envy. He has an extensive knowledge of science, and is a talented artist and designer. He has the habit to invite Gian and Shizuka to something or someplace, but always leave Nobita out with one excuse or another.

In some scenes, Suneo is seen as a narcissist who loves to stare at himself in the mirror while telling himself that he is the most handsome guy in the world. He is still a bed-wetter and needs to wear diapers when he sleeps, despite being in the fourth grade. He considers this humiliating habit his secret weakness. Suneo is also very self-conscious about his height, being the shortest kid in his class.