Then there was that song that basically described Greysior's lover Hachiko-ing away for the rest of her life on the isekai side of the gate.
I wonder...the Uribou/!Olmasior wolflady seems to feel fate has events in motion, and she's gone out of her way twice now to show Kazura souls being guided on / laid to rest. Where's she going with that?
Re: the gate, it seems like his Dad knows about the home, but hasn't been there, so then someone else with a connection to it has, and relatively recently.
...are we dealing with a time loop? Perhaps a multigeneration one?
(also, I think we're missing chapters 47.5 and 81.5, if they're relevant)