Kitsune transformation requirements?

[Cauldron]

I'm at a loss as to what I have to do in order to get the option to meet Keros again and do whatever to turn into one. I've freed and married Kiyoko and I've heard you needed to do the metal questline but I've done that and nothing changes. Is there another parameter that I'm overlooking or did I mess something up?

 

[WolframL]

You don't actually need Kiyoko freed, you just need to do the For Want of a Nail quest and the option to bind yourself to Keros should appear the next time you enter the shrine in the Den.

You did turn the relic in to Kohaku, right?

 

[Sikari03]

I also can’t figure out how to get the transformation. I did the quest but the option won’t show up

 

[zagzig]

Nakano gives you two quests. Get the metal relic and turn it in to Kohaku, and then fight the puppets for Rindo. Check back in if that's not enough to trigger the conversation.