Rito is a 15 (currently 16) year-old high-school student and the protagonist of the series.[1] Rito used to be on the soccer team in junior high and was quite good, but quit because he was constantly helping his father with his manga artist duties, thus did not want to leave his sister Mikan alone in the house. Mikan comments he is very good at the most "useless little things", like crane and festival games (e.g. hoops, catching fish, squirt guns). Along with the numerous useless little things Rito is good at, he is also an accomplished florist, gardener, and horticulturalist.

Rito's nature is borderline clumsy, where he always ends up molesting or groping the many girls in the series (though mostly unintentionally). He is extremely kind, selfless, caring, charismatic, and thoughtful and has a lot of respect for women, though mostly by intention, and not so much by success. Due to his shyness around girls, he is very clumsy around women and has great difficulty maintaining his composure around any sort of stimulating situation. Even without interference from Lala's inventions, Oshizu's psychic powers, or Celine jumping into his face, Rito is on his own clumsy enough to trip over absolutely nothing, and possesses an extraordinary skill in accidentally reaching his hands or face into the breasts or other private parts of any girl within reach when he is falling.

It is only by accident that he encounters Lala Satalin Deviluke, and despite his enduring feelings for Haruna Sairenji, Rito shows signs of developing deeper affection towards Lala throughout the story but is unsure if what he feels is actually love. This is shown again when he couldn't help but think about Lala even though he and Haruna were naked together. It is recently revealed that he is in love with Lala, but he is also in love with Haruna. At the end of the series, he confesses to Lala, but tells her he also loves Haruna, yet she is happy on both parts. He is confused as polygamy is illegal in Japan where Lala replied that once he is king of the universe the laws of earth no longer apply and forces him to go tell Haruna (strapping a jet pack to his back). Right before he was about to tell her, she moves out of the way, just like when he confessed to her very early in the series, leading him to state "I love you" to all of the female cast with the exception of Momo, Mikan, Golden Darkness (Yami), and Haruna herself. The ending implies that his "love" troubles will continue on into the future.

Riko Yuusaki (夕崎 梨子 Yūsaki Riko?)Voiced by: Akeno WatanabeAs Riko Yuusaki, his female alter-ego, she is a beautiful girl (with a physical appearance resembling a tomboy) who gets much attention from men, such as Motemitsu, the perverted principal and even Saruyama, Rito's best friend. Later, Saruyama falls in love with "Riko-chan" and asks Lala to invite her for a date; out of pity, she forcefully changes Rito into "Riko" so Saruyama can go on a date with Riko. After that Riko only appears for short amount of times at rare occasions.

Mikan Yuuki (結城 美柑 Yūki Mikan?)Voiced by: Kana HanazawaRito's independent and reliable 12-year-old sister, Mikan takes care of the housework while their parents are away on business and watches after Celine. In contrast to her brother, she is very mature and does not hesitate to tease him, going as far as stating they aren't blood-related, but quickly retracting the statement, playing it off as a lie. Mikan also seems to have a certain lack of respect for Rito because of this (she hardly ever addresses him by his honorific as an older brother), but does refer to him as "Onii-chan" as thanks for trying so hard to take care of her when she develops a fever[2] and when he gives her a Christmas present. Mikan may not show it, but she cares very deeply for Rito and misses his company, to the point one could suspect her of having a brother complex. This is more evident in the second OVA where she wonders if he would marry her if they were not blood related, and in the manga where she blushes every time another character mentions her brother, and also in the 5th OVA where after being hit by the pollen she tries to molest him while affectionately calling him "Onii-chan". Her brother complex may be the reason she rarely calls Rito "Onii-chan"; less a lack of respect and more a sign of her wish that their relationship was something other than that of a brother and sister. She also states how she and Rito used to play together before Lala entered their lives.[3] 

It is later revealed that Mikan is terrified of thunder and lightning (and that Rito would always comfort her).Mikan grows quite attached to Golden Darkness, perhaps due to Darkness seemingly being the same age as her. 

Mikan is very perceptive and seems to be able to read people's emotions, even their reactions, most of which is Rito's obvious anxiety around Haruna and Yui's subtle feelings for him. Mikan even calls him a "playboy" (as does Nana) for attracting so many girls all of a sudden. Mikan, however, does respect Rito's relationship with Lala, even going so far as to tell Momo not to get too close to Rito for Lala's sake, although it is fairly obvious that she could have done this out of jealousy from how close Momo was getting to Rito.Mikan appears with Celine in the series Mayoi Neko Overrun! as customers in the manga series chapter 1 and with some friends in chapter 3.Saibai Yuuki (結城 才培 Yūki Saibai?)

Voiced by: Keiji Fujiwara Rito's father is a manga artist and is very different compared to Rito in terms of both looks and personality. Saibai draws at amazing speeds and can be utterly serious before deadlines are met, but seems to have a bit of a goofy side, such as making a joke about Rito and Lala "sleeping" together every night and punching Rito when he got drunk and mistook his son for a burglar. With the help of Lala he returns for the Christmas party, stating how much Zastin and his workers have grown since starting out. In the anime, he writes a (not-so-encouraging) letter to him at the end of the first season.

Ringo Yuuki (結城 林檎 Yūki Ringo?)Voiced by: Sayaka OharaRito's mother is a fashion designer and a scout for fashion models. Normally working overseas, she returns home to check up on the family. Despite initially appearing to be refined and chic, Ringo's personality is equally as odd as Saibai's, where she has a tendency to start sizing women up with her hands, whenever she spots pretty girls. Ringo seems to take her work very seriously, having immediately entered "work-mode", when she meets Lala and Haruna for the first time.[4] Like her daughter, Ringo is also highly perceptive, able to read Haruna's feelings towards Rito. With the help of Lala, she returns for the Christmas party and mistakes Celine as her son's child.