Remember the boyfriend Chihaya Mifune mentioned in her Coop video? She wanted to know how the Protagonist got rid of him.
That could be the sidequest “Beware the Annoying Boyfriend!”, in which you get to deal with Kanahiko Nakanohara’s obsession over controlling his girlfriend. Chihaya probably asks the Protagonist to save the girlfriend.
the weird pattern on Chihaya’s dress makes a lot more sense when you take the Fortune card from the previous games, delete everything but the black outlines, and realize that’s exactly what Soejima did.