You know, I've always hated the reasoning of the champion during soulbinding scene to Keros. It always made the champion sound ignorant, whiny and stubborn - "DUN CARE, SHUT UP, MUST MAKE FLOOF HAPPI HERP DERP".
I prefer my own headcanon as to why my champion does it: sure, it is nice to be like Kiyoko and my other fox lovers, but the real whole point was to pull my soul out of Kas's reach, even if I did like her - She still a demon with an obsession, always that nagging voice in the back of the head saying "she really only cares about your soul" and if you soulbound and she finds out, it's kind of proven. I always activate the halloween Kas date before soulbinding because of what happens at the end if you sleep - I think it's a good lore hook to cement the fear of jumping off that particular cliff.
Also, being inside yet outside by being a soulbound made floof is hilarious to me. The shit the champion can get away with in their position is worthy of the Trickster.