I think some inherent comfort of the party’s relationship, of why they’re so tightly knit and wholesome, is that it’s kinda the embodiment of "people that care for each other unconditionally, so much so that you could be the biggest freak on Earth and they would still not turn their back to you". Like, Laios’ whole character arc is that he was scared of others and their judgement, that he should hide a big part of himself and his interests to be tolerated if not accepted… But showing himself to others was the road through which the party bonded and got closer, and by the end of the story Laios literally turns into his monster because it was his biggest wish and everyone sees it and also he eats his human body a lot. After that he runs to the woods and is so scared of everyone not wanting to see him again, but y’know what. It’s fine his party still loves him, and aghhhh ouch my heart

I think also, Izutsumi was central to the party having a found family feel. The party was mostly made of work colleagues acquaintances, but adopting a stray/teenager that has no one on the way in your grand adventure really makes the whole family vibe skyrocket.