Yuy, Heero

ヒイロ・ユイ

Heero Yuy is merely a code name, derived from the fallen Colony leader whose assassination the Gundam Pilots were meant to avenge.
Upon arriving on Earth, Heero meets Relena Darlian, the daughter of an Earth/Colony peace advocate. After enrolling in her school, Heero saves her life on multiple occasions, which causes him to confuse his mission with his feelings.
His first ally is Duo Maxwell, who assists him in retrieving his Gundam from the ocean. Subsequently, he operates independently for a period, attacking bases and OZ encampments.
His main rival is Zechs Merquise, and they engage in several battles throughout the series, occasionally exchanging Gundams. His other rival is Treize Kushrenada, who gives him the purely evil Gundam Epyon, which Heero trades to Zechs for the Wing Zero.
Although Trowa Barton is the most mysterious regarding his personality, Heero comes in a close second, consistently disappearing after completing a mission or having an encounter. He lives by his emotions, as he states several times in the series, and usually thinks things through. He was also referred to as "the heart of space" by Quatre Raberba Winner, Pilot 04, near the end of the final episode.
In Frozen Teardrop

Spoiler