Yūki Mikan is Rito's independent and reliable 12-year-old sister. Mikan takes care of most of the household work while their parents are away working and also watches over Celine. In contrast to her brother, she is very mature and does not hesitate to tease him, going as far as lying that they aren't blood-related, but quickly retracting the statement and telling the truth. Mikan also seems to have a certain lack of respect for Rito because of this (hardly ever addresses him by honorific as an older brother), but does answer him "Onii-Chan" as thanks for trying so hard to take care of her when she develops a fever and when he gives her a Christmas present. Mikan has grown quite attached to Yami, perhaps due to Yami 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 Sairenji Haruna and Kotegawa Yui's subtle feelings for him. Mikan even calls him a "playboy" (so does Nana) for attracting so many girls all of a sudden (even though she attracts so many boys at her school). 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's possible that she could have done this out of jealousy of how close Momo was getting to Rito. Mikan is the only main character that doesn't attend Sainan High. Mikan has gold brown eyes and brown hair, she is described to be really cute by some characters. According to a "Full size Dakimakura Cover-Mikan Version", her measurements are B70-W52-H73. Mikan is usually seen in an apron, as she is in the kitchen most of the time. Other than cooking attire, she is seen in a school uniform, casual clothing, etc. As a younger sister, Mikan is widely known for her maturity and reliability for her age. Her maturity is also quite unique, as while she is Rito's younger sister and the youngest character in the cast, she is arguably more adult than most of the other characters, and basically acts as a big sister, wife, or mother to Rito and all who live in her house. Because she is very good at cooking and housework, she essentially takes care of her big brother. Rather than looking up to him, she instead treats him like he is her little brother, and rarely calls him "Onii-chan", as she used to. Mikan generally treats Lala the same way, enjoying her company like a little sister and pleased to see her brother's life becoming more entertaining upon her arrival. Like most girls in the cast, she is also aware of her breast size and often feels inferior when comparing other girls' to hers, mostly Lala, although her physique is quite normal for her age. Despite this, she still feels insecure about this, and has developed a positive connection with Nana due to their similar chest-related angst. In the fifth OVA, when Mikan was effected by the pollen of one of Momo plants that makes anyone who inhales it to act freely, she acted childish and clingy towards Rito, even calling him "Onii-chan", showing how shy she is at expressing how she feels towards Rito and that she just acts mature around others. She even feared that her place in Rito's might slip away when Momo was being too close to him. Mikan is very perceptive, as she is good at understanding other people and noticing their feelings. She knew very quickly her brother's crush on Haruna, and Haruna's similar feelings for Rito as well. And she knows that Rito is too scared to enjoy perverted things, and that Lala is innocent and quite childish, so she doesn't mind catching Lala naked in her brother's bed in the morning and even treats it like something normal, though it should be noted that she overreacted once when she mistook them having sex in his room, when Lala was just moaning because Rito's hand was stuck to her tail. But she particularly doesn't like Momo sneaking into his room at night and sleeping with him, because of how sexual she can be towards him. Like a big sister or mother, she would try to protect Rito from sexual temptations and doesn't like it when girls with more perverted tendencies like Momo and Mea would do perverted things to him. She tries as often as she can to watch out whenever Momo gets the opportunity to be alone with Rito and even guards his room at night to stop her from sneaking in and sleeping next to him. She also doesn't particularly like Mea when first meeting her, and though she tried to get to know Mea better after learning that she is Yami's sister, she finds that she cannot deal with her type and likely can't become close friends with her as she is with Yami. Mikan seems to get along quite well with characters who are more level-headed, composed, and mature, such as Yami and Kujō Rin. In To LOVE-Ru Darkness, despite being older than even Mikan's big brother, Rin seems to have become friends with her, and is astonished that someone like Mikan is the younger sister of the clumsy and quirky Rito. And Mikan is the only person whom Yami truly considers to be her friend. Rito explains that because she is so mature and reliable for her age, deep down, Mikan can get lonely without people she can relate with, and so she can use older friends who are like big sister figures to her, whom she can lean on. Mikan has a case of Astraphobia, the fear of thunderstorms.