Seizing the village's coal mines to fuel their ships, the Fire Nation extracted exorbitant taxes from the citizenry for five years, and most cruelly, took all known earthbenders to a sea platform prison, Haru's father, Tyro, being among them. To ensure his safety, Haru's mother forbade him from earthbending, although he continued to practice earthbending in secret, as a way to feel close to his father.
During the late fall of 99 ASC, as Haru was practicing alone, AvatarAang and his friends stumbled upon him. Later, when Haru and Katara struck up a kinship over shared parental losses, they came upon a villager trapped under a rock slide. Haru aided him through earthbending, but the old man betrayed him to the Fire Nation soldiers and the young earthbender was taken into custody.
Aang and Sokka helped engineer Katara's false arrest for earthbending, so she would be taken to the shipyard. There, she and Haru helped stir up a mass prison rebellion and escape. Reunited with his father and reinforced by fellow earthbenders, Haru had a chance to drive the Fire Nation away from his home.
Following their escape, Haru and his father indeed helped to liberate their village from Fire Nation control as a part of the Earth Kingdom rebellions.
Haru was one of many familiar but slightly changed faces recruited by Sokka to help in the Day of Black Sun invasion; he now had a mustache and goatee. Haru and his father were part of the ground forces attacking the Fire Nation capital. When the submarines were destroyed, the warriors decided to surrender; Haru then promised Tyro that they would return to rescue them. The young people, namely Aang, Katara, Sokka, Toph, Teo, The Duke, and Haru, escaped on Appa and traveled to the Western Air Temple.
Haru had befriended both Teo and The Duke since the invasion, and upon arrival at the Western Air Temple, he and his two friends began to explore the sanctuary. They found it to be the perfect place to hang out and for Haru to practice earthbending.
Haru stuck with Aang's group until Azula and an air fleet attacked the temple. He fled along with Hakoda and his friends while Aang's group flew off on Appa.
Shortly before the arrival of Sozin's Comet, while the team was having dinner, Katara announced she had a surprise, and Toph quickly assumed she "had a secret thing with Haru", only to be met with an awkward silence from everyone.
Haru was seen during Zuko's coronation after the Hundred Year War ended, finally reunited with his father once again.
Haru was a skilled earthbender. He preferred earthbending with his hands unlike most earthbenders, who preferred to earthbend with their feet. He and four other earthbenders, including Tyro, created a shield strong enough to withstand a combined blast from several firebenders. Together, he and Tyro were able to compress a large amount of coal into a single projectile, a difficult feat to accomplish.
'Haru' in Japanese means the season 'spring' (春) and in Korean means 'one day.' Haru meaning "spring" in Japanese could be a reference to him being an earthbender since earthbenders' dominant season is the spring.
In The Last Airbender, Team Avatar was captured by the Fire Nation after trying to rescue a young earthbender from Fire Nation troops, but they failed and were placed with him and his father in a compound where the earthbenders from his village were interned. He reunited with his father and threw the first blow in the liberation of his village after an inspirational speech by Aang. Although the boy was never named and was significantly younger than Haru, his story was mainly based around Haru's.
During his Day of Black Sun mission briefing, Sokka humorously said that Haru "now [had] a mustache", an inside joke about Haru lacking facial hair during their first meeting.