I mean their relationship is still there. Just because they remembered their past doesn't mean that the life they've lived until now is meaningless. "Yuu" (real Mika) still cares about Guren, his friends and obviously "Mika" (real Yuu/the eye).
I assume "Mika" (real Yuu) still cares deeply about "Yuu" (real Mika), too. If anything just from the fact that The First told the real Mika that giving the eye a name "curses them with a heart". So even if "Mika" (real Yuu) isn't technically a being, they've still created a connection between each other...
Girl, idek. This shit's complicated.
I feel like the only thing that's changed is basically them realizing how much bigger the picture is, and that "Yuu" (real Mika), not only wants to save everyone, but also The First.
At the end of the day, all I know is I'm sailing on this ship across the entire ocean LOL
No way they built their relationship so much just to make us look like weirdos