Name: Heero Yuy
Age: 15 (TV series), 16 (EW OVA)
Height: 156 cm
Weight: 45 kg
Nationality: Japanese
Hair Color: Moss Green/Brown
Eye Color: Prussian Blue
Family: No known living relatives
Home: L1 Cluster Colony
Pilot(ed): Wing Gundam, Mercurius, Epyon Gundam, & Wing Zero Gundam
Seiyuu: Midorikawa Hikaru
English VA: Mark Hildreth
Often referred to as the "Perfect Soldier", Heero proves throughout the series why he has the honor of being known under that title. Code-named after the martyred colonial pacifist who died at the hands of Odin Lowe in AC 175, Heero has been trained under the tutelage of Doctor J to be a ruthless, effective killing machine void of all emotion for Dekim Barton's "Operation M/Meteor". This lack of emotion combined with his lack of self-worth drive him to stop at nothing to fulfill what he must do, even going so far as to risk his own life and his Gundam in order to do it. His apparent "suicidal tendencies" during the first half of the series show that he will do whatever it takes for the mission.
Throughout the series, however, Heero loses much of the sadistic, insane, homicial image he presents himself with in the first episode. His reluctance to kill Relena Darlian Peacecraft numerous times and the remorse he has when he made the grave mistake of killing General Noventa and the other pacifists on board a shuttle are examples of his gradual loss of the callous, unemotional being that he was molded into being. He gives up on his death threat (which, by the way, he never seems able to carry out anyway) to Relena, opting instead to "protect her". By the end of the TV series, he is more 'human' emotionally than he was at the beginning, the point being proven when asked by Zechs why he did not kill him: "It would make Relena sad..."
His renewed sense of humanity and gain of self-worth during the series help to curb the rather drastic measures of fulfilling his mission he undertook during the early part of the TV series. During Endless Waltz (OVA, movie, and manga), Heero appears to show genuine concern for Relena when he tells Duo about her disapparence,in addition to making a desperate attempt to make Wufei realize the errors of his way while under Mariemaia's command was wrong during their battle and sparing the life of Mariemaia Barton Khushrenada when he finally sees her face to face. It also leads him to remember the accidental death of the little girl during a mission to blow up a weapons factory and feel the remorse that Doctor J thought he managed to rip from Heero's soul prior to executing Operation Meteor (M).