@TheGTF
At the core of this is issue is the question- Is Yafya a true well meaning "hero" with a morale compass who's trying to do right by everyone in his own way? Or is he a self serving asshole? There is evidence for both.
There is evidence that Yafya is not interested in glory, and was disappointed in Gosha because because he wants to make a better world, and with Gosha at his side as an equal, he is better able to do so. This interpretation does leave Yafya with a axe to grind with Gosha, but unlikely to put it on Legosi. In fact he may see Legosi as Gosha number 2, a second chance to have someone at his side to help him improve the world, and a younger person at that with him feeling his age. They've hinted at this near to the point of outright saying it that Yafya would like Legosi at his side, as a aid and possible future predecessor. That is why he offered him lots of money and aid with the marriage legality issue too. And with this interpretation, even if Gosha has deeply disappointed Yafya by what feels like abandoning him, they are still deeply friends, non-romantic ex-soul mates, which made the feeling of abandonment sting all the more. And we know that Gosha has mad skills like Yafya and it would be bad news for Yafya to piss him off by getting his grandson killed, really bad news for Yafya. Yafya wanting someone at his side, not a powerful enemy which at the very least would slow him down and distract him from the things he wants to accomplish. All that is the positive interpretation, which I am leaning towards.
Also there is the element of the story that Kirin-kun alluded to that the story seems to be all about Legosi's journey to become prime Beastar along with possibly the buck whos name I forget as a partner. The current Prime Beastar seeing him as future Prime Beastar fits with that narrative.
So given all this, why is Yafya no where to be found? Don't know, a test? A failure of judgement or of keeping a close enough watch on the situation to be ready to get in?
There does seem to be a twisted side of Yafya too, aside from burying carnivore corpses in his garden (which I do not think would make for good fertilizer, has he never heard of manure?) Hopefully they weren't explicitly murdered for this purpose.
@Kirin-kun
So far the single hybrid we've known him to know, the only one in the story if you don't count Legosi himself (but he's only a quarter who completely passes off as 100% wolf with the only difference being immunity to poison, and not a herbivore/carnivore hybrid with the story implies is more extreme) he's not gotten along with AKA he's not gotten along with Melon.
The story seems to be implying that herbivore/carnivore hybrids are destined to be messed up psychopaths (maybe unless raised extremely carefully?) both through Melon, and through extremely judgemental prejudicial things Yafya has said. And it's not just things he said for himself, he implied it was a serious crime for herbivores and carnivores to mate at the party. And the party being super secret with the passwords and being underground and all that also suggests that. I really dislike this message, I think the stories logic for this is really messed up and nonsensical. I hope it's not based on some RL prejudice from the author about mixed "race" humans. This statement of Yafya pissed me off the most and made me think badly of him, but now I see the message is coming everywhere from the story, not just Yafya.
@Hjerpe
Well they could just give the racket up or choose one of their own like before. The main reason they choose a herbivore (or perhaps someone who could pass as one AKA Melon) is so the herbivores they deal with don't struggle as much. But Legosi is obviously not a herbivore.