Ando Masahashi was a co-worker of Hiro's when the show began. He was initially skeptical of his friend's powers.
Soon enough, though, Ando was made into a believer. He became Hiro's trusted sidekick and was also one of the few characters on Heroes without any special abilities/
In chapter three, the friendship between Ando and Hiro is tested. The latter has a future vision in which the former murders him. That would put a strain on any relationship.