Tsukiyomi Ikuto

Picture
Name Ikuto Tsukiyomi
Kanji 月詠イクト
Birthday December 1
Blood type AB
Age 17 (in chapter 28 he told Amu he was a senior in high school)
Height 180cm (5 feet, 11 inches)
Weight 64kg (140 lbs)
Team Easter Company
Japanese Voice Nakamura Yuuichi

Appearance:
Ikuto has blue hair and eyes. He is taller than Amu Hinamori and Tadase Hotori.
He wears a choker with a silver cross. He is most often seen in his black school uniform, but he has been seen in other black (or indigo) outfits.
                                                                    

    Personality:
Ikuto is enigmatic, aloof, stoic and a little naughty, much like an alley cat. He can also be sweet and kind. He likes teasing people, especially Amu and Tadase. Ikuto is selfless and protective, thus, he is willing to distance himself from those he cares in order to protect them and stop them from getting embroiled in his own troubles. This explains why he kept himself away from Utau after she allies with the Guardians. Another example of this is when he makes fun of Tadase so that he'd be hurt and make Amu hate him, so ultimately they [Amu and Tadase] would not meddle with his troubles with Easter (especially Amu).
Although Ikuto may seem to have a passive personality, he is quite perceptive and honest.
As for chapter 43, Amu states that Ikuto "loves music... and his dad". 

History:
Ikuto is a teenage boy contracted by Easter to find the Embryo. He often helps Amu Hinamori even though he works for the Easter Company. Ikuto actually despises Easter and tries to wrench himself free from them by trying to find the Embryo to grant his own wish. By chapter 43, he had left Easter Company in search of his father. In the third season of the anime, he is already traveling the world to search for his father and therefore is absent from the series.  
He is in possession of the Dumpty Key. It pairs with Amu's Humpty Lock, which comes together in chapter 36/37.

Like his father, Ikuto is a skilled violinist. His mother, upon marrying someone else after they found her husband's violin in a foreign country and believing that he would not come back, bound her children into working for Easter.

Ikuto is in love with Amu Hinamori, confessing it in chapters 28 and saying it in 43 of the manga. He also kissed her on the cheek before taking off in chapter 43. He confessed to her in the anime the same time Tadase did, but Amu thought it was a joke.In Chapter 28, Ikuto told Amu to grow up faster because he wanted Amu to catch up to him.
In the anime, after he leaves Japan to search for his father, Ikuto keeps in touch with Amu, Utau and Tadase.