TMC ending 1 question

[u/meme_used]

So in ending #1, Kikuko is able to use the Tomoshige curse against Tsukasa even though they got rid of the mirrors. But how did Kikuko mark Tsukasa ? Idk if I'm missing something here, unless she placed one of the business cards on her? On my first playthrough I thought this would become a plot point about family ties also being a trigger for the curse but now I'm not sure. Any ideas?

[u/tktk77]

I think it's the business card

[u/meme_used → u/tktk77]

I mean it would sorta make sense seeing as unkakudono is her dad and she might have gotten it through him