This was obviously placed there intentionally as a seemingly innocent element that could turn into a devestating feux pas if the story was ever retold by a drunk Yui in a wedding toast to honor the union between Ayano and Kyoko. Personally I don't think the Chinatsu thing can compare since Kyoko is the boylesbian.
Yes. Boylesbian. &3wn?
Usually you'd say seme.
Yui doesn't need anyone.
She can boylesbian with Kyoko and Chinatsu. You only care about cheating if you're competing in the same event.