Kei's grandfather, Kaname Takishima, is the head of the Takishima group and is a powerful man in a business world. However, he is rarely seen by others, including his own family members. He makes his first appearance in chapter 25, when he makes a phone call to Kei's father. When Hikari speaks with him over the phone, he plants the idea in her head that Kei is burdened by her very presence. She meets him face to face in Chapter 59, when President Takishima tries to convince Hikari to transfer schools. He disapproves of Kei's relationship with Hikari and makes many attempts to separate them, such as sending Aoi, arranging marriage meetings for Hikari in London, and arranging a marriage between Kei and a girl named Alisa. The President expresses a strong dislike of Hikari and the mere sight of her sickens him. It is eventually revealed that he feels that he and Hikari share similarities that will make the people they love suffer; as a result, he fears that if Kei remains with Hikari, he will endure the same fate as his grandfather did. (Source: Wikipedia)
She is Aika's salvaging partner and her Boss' daughter. Her mother divorced after she was born. She wants to run the business better, but her father keeps to his policies. She does not like being left out of transactions nor having Aika do the work herself. Rion looks upon Aika like her real sister and yearns to become like Aika. (Source: Wikipedia)
A beautiful girl with unbelievable strength, Nagi is Kei's cousin and is a year younger than him. She appears during a brief vacation the SA take at Akira's villa, where they intend to celebrate Kei's coming birthday. Extremely arrogant and full of pride, Nagi proclaims herself to be Kei's fiancée and loves him very much. However, she quickly becomes jealous of Kei and Hikari's closeness with one another and ends up acting unpleasantly towards the rest of the SA in order to get Kei's attention. Upset that Kei, the only person she feels comfortable around, cares more about Hikari, Nagi tries to get rid of Hikari, who comes to see that Nagi only wants to please someone she cares about. Afterwards, the two reconcile and become friends. (Source: Wikipedia)
Izumi Takishima is the mother of Midori Takishima and wife of Kaname Takishima.
Sui is Kei's younger brother and resembles a younger version of Kei. Initially, he dislikes Kei because he finds living with him disgusting and thinks of him as a robot wearing human skin. Because Sui feels very inferior to his brother, who is good at everything, he believes that he cannot reach Kei's level and he refuses to take his studies seriously. However, when he sees that even his "perfect" brother can become desperate and caring, Sui develops a huge brother complex. Sui likes to call Hikari "Stupid Girl", but approaches her frequently when he thinks that Kei needs help. He is in grade 6, class B at Hakusenkan's elementary school division.
Sakura is the daughter of the head of Ushikubo Medical Manufacturing Group and is Kei's first marriage meeting (or omiai) partner to appear in the series. While she does not consider Kei her type, describing him as a "dark lord" rather than a "prince", she considers him a possible marriage partner because his abilities would be advantageous to her family's business. Sakura hates dishonest people with a passion, and her family's motto is centered around honesty and punishing/loathing dishonest people. Hikari's straightforward and honest nature allows the girls to become friends. She attends the same school Yahiro does and sometimes plans stuff out with him (whether the plans be good or evil). Sakura falls in love with Jun at first sight, as he fit her ideal of someone who was a "prince", and accepts his split personality. She begins to date Jun soon after; however, because of her forceful personality, she is uncertain if Jun reciprocates her feelings until he admits to her that he does. Sakura first appears in volume 4.
Finn is the prince of a small country, in the last episode the time when Ryuu looked up while hugging his dog there was a person in the window, it was him, but this is never mentioned. This is because due to the ordering of the anime, he is unable to appear, and there cannot be a season 2. whose true gender has been concealed from the public. She initially appears as a reluctant participant in a series of arranged marriage meetings Kei's grandfather sets up for Hikari. When Hikari flees from the meeting, Finn falls for her on the spot, since Hikari fits the exact description of Finn's ideal person: a woman with long dark hair possessing a sweet yet tough personality who wears a red dress. After helping Hikari escape, Finn follows her to Japan with the intention of proposing to her. The SA later discover that Finn's mother fits the description of the ideal person Finn wants; Hikari tells Finn that it's a wonderful thing to look up to her mother so much before adding that she and Finn can still be friends. Afterwards, Finn enrolls in Hakusenkan and tries using Ryuu to get closer to Hikari, but ends up becoming very good friends with him. (Source: Wikipedia)