Hikaru and his brother Akira are brought to the USA to see the first showing of their father's invention for Stark Enterprises: the DISKs, small devices to imprison villains in a codified form. After Loki Laufeyson captures the Avengers and other heroes in DISKs, Akira, Hikaru and other three kids are affected by a defective bio-code that allows them to briefly summon the heroes from the DISKs, via a D-Smash. Hikaru's bio-code allows him to D-Smash Energy heroes like Thor.
Hikaru is very good at several activities, but he can get distracted if Akira is in danger. He has bonded with Thor over both habing issues with their respective brothers, Hikaru being afraid of losing his in a dangerous situation, and Thor sad of having lost his to evil.