Son Nathan is no stranger to the Supernatural, being the second youngest child of the Son family, younger brother to Son Gohan and older brother to Son Goten, and second son of the great Son Goku, pretty much explains how much he knows about it. Though if you were to ask him directly, he would start off with him explaining that he met two people one day in the forest when he was a child, as he seen them showcase abilities no normal humans can do, but he hasn't seen them in years due to circumstances with people wanting to destroy Earth, as in time, he ended up forgetting about them, not knowing that he might one day see them again.
Years later, he was heading to a place to train, after hearing that his dad is coming home for one day, that day being on the tournament, he wanted to show his dad how far he has come, hoping to impress him. However, before he could train, he was bumped into by a group of five girls who appeared to be running from some people, so he hid them behind some rocks and quickly dealt with the pursuers. Little did he know that this small chance encounter, would change his life in a way that would far different than normal.