I'm guessing people think this is completely random or non canon (I can't verify that it's completely canon but at the very least it's a real spin-off) since it has almost nothing to do with Naofumi and basically has a Re:zero situation, IE resetting every time certain people die. There is an explanation for that, first of all Motoyasu being the way he is, such as calling Naofumi father, hating women, and being in love with Filo and Filolial's in general, is because Witch betrayed him almost as bad as how she betrayed Naofumi. About why it's restarting every time a hero dies, that's what makes it a spinoff. The localization of the LN hasn't gotten that far so I'm basing it off of the WN which has the same general direction but in the original WN ending the goddess or whatever she was sent the heroes back to their own worlds except for Motoyasu who ended up in an alternate version of the world everyone reincarnated to. That's as far as the WN went so if the general direction is still the same then the LN might explain how that happened.

tl;dr Motoyasu went bonkers and by the end of the WN ended up in an alternate version of the world everyone reincarnated to where time loops