Board Thread:Questions and Answers/@comment-37328639-20181028101709/@comment-26411685-20181029033117

I think Satous's skills and titles may play a part, but the main reason comes down to:

Satou actively power-levels his companions by having them to scratch a target so they have a share of the exp, before killing the target himself immediately afterwards. This goes against the common-sense of the world, since normally people would be against having their exp "stolen" while they are the ones who risked their lives and did the majority of the fighting.

Even when people use the same training tactic as Satou (i.e Weasel-kin Empire), Satou is still far more efficent due to his ridiculously high level allowing him to target demon lords or other legendary beasts. As a result, the exp gained by his companions would also be very high.

Later on when Satou's companions are strong in their own right, they could power-level themselves by fighting large mobs continuously. During this time, Satou provides his companions with god-tier equipment and almost unlimited recovery items. This means his companions can power-level efficently because they can safely fight stronger enemies (which provide more exp) than people of the same level normally would, and with very little rest.