Did he have relations with that person who died on the incident?

probably his dad? cause his parents died, right?

I thought that was his prev guide? Or noh?

i think it was like his mentor or something ? he became like a father figure to him after his parents died

it was the former captain of the team

Mentor/original leader of the team. It's sad bc he was parental figure after his parents died and he came to to esper.
I did not like this part in book when it turns out that every time he uses his powers, he's reliving death of his loved ones, parents, mentor and guide