Often bubbly and bright, Yuki's character can charm even the most sour of personalities. His boyish good looks have even attracted animal and humans alike. Yuki is also down to earth, as he grew up in a poor household and had to do many ordinary chores. He always tries to befriend each person, and is extremely loyal to his friends, even going as far as to pose as a girl for Kyohei and Sunako. Yuki's temper is almost non-existent, and is mostly tolerant, however his temper has been known to surface whenever a friend is insulted or threatened.
Yuki also occasionally resents being thought of only as "cute", but his attempts to counteract this have only met with people viewing him as even cuter than before. His effeminate appearance has allowed him, usually very reluctantly, to convincingly dress up as a girl. It is shown that he does not deal with scary items or situations well, causing Yuki to avoid Sunako's room (this particular feature has been exploited by an old woman, whom Sunako calls "Granny", who owns a horror-themed museum).
Yuki can easily be seen as one of the more normal and well adjusted characters of the series. It is shown that Yuki had a poor, yet happy, family life. As the series progresses minor plot points are designated to showing flaws or character building for him.
Yuki grew up in a poor family, and initially took charge of the chores before the arrival of Sunako. (One minor plot hole in the series is that while Yuki was initially shown doing chores with no apparent difficulty, later in the series he is shown as being incredibly inept at the same duties.) He ends up living at the Landlady's mansion because his mother and the Landlady happen to be friends.
After Sunako entered the household, Yuki is often seen taking a commanding role in tutoring Sunako in the proper ladylike behavior. Whenever Sunako becomes too upset to cook, Yuki is usually the first to attempt to cook in her place, but is abysmally bad at it.
In a recent chapter, Yuki's family makes an appearance, including his four-year-old twin siblings, resulting in quite a bit of chaos in the mansion.
So far in the series Yuki is seen as the most most personable and approachable of the four. He makes friends easily and genuinely. He is also the only one in the series that initially had a girlfriend. Yuki's relationship with his girlfriend Machiko is frequently tumultuous, with the two having an on and off relationship. Machiko, who is identified in the manga as being a student at the all-girls high school next door to his, is not shown in the anime as Yuki's girlfriend but has a cameo in the school fair episode. From a bonus page at the back of Volume 2, is it revealed that she was the invention of mangaka Machiko Sakurai (桜井 まちこ, SAKURAI Machiko), creator of the mangaMinima!(ミニマ!, Minima!) and one of Tomoko Hayakawa's colleagues.