Well theres a few actually for different reasons. Not sure if Yuki can fit them all though!
1# snakes! Big long throat! (Like literally all throat!) And really cute bulges of prey! And that seductive coiling and Hypno really makes it sound amazing ~
2# big strong dragon! Dragon! Dragon! Dragon! Big belly! Hungry! Yuki just a small snack to them and he's all smugg and teasing about going to eat him hole in one bite and that Yuki will bearly fill him! Sits in a pile of gold and eats kolbolds casually! Yes yes yes!

3 this one is unexpected probably! Plush vore is great! Comfy and warm! Maybe a little Hypno! And sliding down a soft plush and fabric maw into a warm and cozy plush tummy were it's just like the best bed in the world sounds dreamy~

Well that's a short list of top 3. Hope that's good ^^ <3
Wonderful questions ~