It's gonna be another cockblock. She's gonna be nervous, and then freeze up, and then because the guy respects her boundaries, he's gonna back off. No straight up communication about his sexual desires, and this is gonna drag on for several dozen more chapters "until she's ready." No actual sex happens in the story, the ending is they get married, and then a timeskip where they have kids.
I doubt MC will die.
I still half believe that MILF said that because the onyl man she was in that relationship died, we don't know, could have been natural causes or a incident and for her youkai mind she thought it was a consequence of the 2 doing it.
This for me can only change if now MC does sex with Yachiru, because so soon after the MILF comment would mean something trigger and MC wil lhave to find a solution to the curse, if they 2 get interrupted the chance will stay 50/50.
if she wove her hair into it somehow, maybe. probably wouldn't work if it's just tied around it, but actually like molded into the shaft.
then again it could be the wrong material so it wouldn't work like her clothes do.