So... he just disappared from his parents for 4 days... grew 4 years older and got a monster-companion... plus, what if the coming training is even more time? Like... disappearing 14 days and then coming back being an adult... imagine the parents and girls faces... xD
And the dead parents or whatever in the end, authors always think mysteries are intresting... but they dont get how they work... just showing unrelated stuff and not explaining shit isnt mystery, its just annoying xD (And if its MCs parents, summoned to that world of the god-guy and died there and he says "must be karma", wouldnt that imply that he thinks MC and parents deserved it, not to be in the same world, having to live without child/parents?)
At least he does look good... so there is that...