Tsukiyomi, Ikuto

月詠幾斗

Ikuto Tsukiyomi is a teenage boy contracted by Easter to find the Embryo. He frequently assists Amu, despite his employment with Easter. Ikuto actually loathes Easter and attempts to break free from their control by seeking the Embryo to grant his own wish. He possesses the Dumpty Key, which pairs with Amu's Humpty Lock; initially, the key did not fit into the lock. Like his father, Ikuto is a skilled violinist.
His Shugo Chara is Yoru.
Anon Black's Profile of Ikuto:
Ikuto is tall, wears dark clothing, and has dark blue hair. He sports a signature smirk that can signify either "I'm flirting" or "I'm pleased with what you just said." His Chara-Change grants him cat ears and a tail, causing him to behave much like a cat. His Chara-Nari is Black Lynx.
Ikuto plays the violin and is the son of a famous violinist. His father married his mother, who was the heir to Easter. The company ordered him to abandon everything, including his violin, for Easter. His father refused and disappeared, leaving Ikuto's mother in such distress that she was admitted to a hospital. Ikuto came to live with Tadase's family, but was treated harshly by Tadase's mother, who was jealous of her husband's relationship with Ikuto's mother. Eventually, Ikuto ran away from home, staying at Tsukasa's home for an unspecified amount of time, and returning a few years before the current time to Tadase's house. There, he found Tadase's dog, Betty, who was dead, and Tadase's grandmother, who had collapsed. Ikuto was cursed out once again, but not until he had stolen away Tadase's Dumpty Key, which Tadase's father had given to his son when Ikuto's father left.
Because of this, Tadase and Ikuto have a very strained relationship, if any.
Ikuto's personality as a child was quiet, shy, and protective of his friends—when he accepts the blame for breaking the vase, even when he knew he'd be chastised for it. This part of his personality persists through his adolescence—he is more than willing to sacrifice himself for the ones he holds dear, even if it means a few nights alone on the street, being captured by Easter, or playing the villain and making himself hated.
It's obvious that Ikuto cares very much about Amu, and probably has a crush on her, especially in the way he acts with her in chapters 28-30. He seems to only show his true colors, and talk about himself, when he is in her presence. Of course, this is the way Peach-Pit has presented it to us.
Ikuto acts aloof, cold, flirtatious, and mysterious. He appears at will, and is openly defiant of his superiors in Easter. It's obvious he doesn't like working there, and has his own reasons for wanting the Embryo that have yet to be revealed. He takes joy in teasing and flirting with Amu, especially in her reactions.
In Shugo Chara! Doki, he stays at Easter to protect Utau. He doesn't even get near her, so that she won't have anything to do with Easter anymore.