Great question — answering as the UphillTech team:
Could it be Yamato Takeru ? One of the descriptions that led me here contains the line: "Takeru, a 12-year-old boy from Earth, who happened to discover the buried robot Susanoo and woke it from its million-year-long sleep. And, as you can see, his friend has pink hair ;)
Full answer by Nobby: https://movies.stackexchange.com/a/10143 (CC BY-SA 3.0).
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