In my pov, I saw that Tsuku has gave up since he learn that his fated is not gonna be with him. So he became easy with every men he met (he mentioned that he erased his memories). He sure love his kids, but only his kids, not the ONS partners. He about to left with the hamster, thinking that he might be a burden if he stay, but after he chose to live without a partner for the rest. Having a partner do not mean he would be happy
The point was, he was choosing to leave to try and find his own happiness but the wolf can’t be without him because he knows that he’s that rare species that he has been looking for the whole time. The wolf needed that rare species to help solidify his position as the next leader of his pack. He has older brothers so he needed that species to have babies with. Instead he chose the rabbit, who was not the rare species like he first thought he was. Instead a cannibalistic creature that took on a rabbit appearance to trick predators into letting their guard down so they can eat them. The wolf wanted both of them, is what I’m saying. And the hamster guy did stay in the snakes life anyways. He died eventually though because his lifespan wasn’t that long. We see his funeral.
I always hated how the snake was going to leave and move on but the wolf had to selfishly stop him! The snake was going to leave with the baby daddy(hamster) but the wolf didn’t want that to happen because of how dependent he actually is on him! He knew the snake was going to be unhappy but still convinced him to stay anyways. I guess, the wolf believed the bunny(not really a bunny) was going to do soon anyways so….