One of the most popular boys at Seika High, Usui appears to take little interest in anything and prefers to observe things as they unfold, though proves to be extraordinarily talented in numerous areas. He develops an interest in Misaki and is the first to learn she is working at a maid café, but chooses to keep her secret and soon falls in love with her. While she dismisses his behavior simply as harassment and teasing (but claims he just wanted to see her "interesting expressions"), he continues to watch over and protect her no matter what it takes like injuring himself in the process, as well as offering insightful advice on how to deal with the boys at Seika effectively and fairly. He appears to be the only male student at school that Misaki is willing to speak to as an equal. Little is known about Usui's background and he is reluctant to speak about it, though he reveals a willingness to tell Misaki. He has an older brother and lives alone in an apartment.

Sung Jin-Woo is the main protagonist of Solo Leveling. Originally an infamously weak E-Rank Hunter, he got the chance of a lifetime when he was selected as the Player of the System, giving him the unique ability to grow in strength without restraint. Jin-Woo is a confident individual with a strong sense of family and a thirst for power. As a result, he is very close to his mom and sister and rarely wastes an opportunity to grow stronger. Despite being strong and respected, Jin-Woo isn't arrogant and is both polite and easygoing in person. He is also mostly indifferent to materialistic desires such as fame and fortune and can be very selfless. In battle, however, he is ruthless, slaughtering his enemies indiscriminately and even somewhat disdainful.