The Fusion counterparts of Yuya and Yuzu (SPOILERS!!!!!

Or Zarc and Ray if we're getting technical)

Serena/Celina:

Yuri:

Apparently from what I have heard (I haven't gotten there I'm still in the Synchro arc), these two don't get that many scenes together. Which is a bit odd considering all the other counterparts do like Yuya, Yuzu, Yuto, Ruri (mainly in flashbacks and motivations though), Yugo, Rin but not these two.

There's probably an explanation why the Fusion counterparts don't get much screen time together

Maybe...