the final trial forced agatha to accept that nicky's death was never rio's fault. sometimes, boys die. agatha never would have kissed rio, showing that she chooses death, without first realizing that.
now that agatha is a ghost, which we know rio will despise, it sets them up for more deliciously antagonistic interactions BUT it also sets them up for healthier interactions than they've had in centuries. when we see them again, their interactions will likely take on a lighter, more playful tone than anything we've seen so far.
because agatha no longer blames rio, and rio was able to take agatha willingly instead of giving her 'special treatment' that would reveal its own cost sooner or later, they're now standing on more equal footing with one another and each is able to see the other more clearly. of course they still have centuries of emotional avoidance (mostly on agatha's part) to sift through, but their main problem was agatha blaming rio for something rio couldn't help, and rio trying to protect agatha from loss by bending the rules for her but really only delaying the inevitable.
agatha needed to accept that rio's role is indiscriminate, and rio needed to accept that agatha is mortal and therefore subject to the same natural laws as any other human. this new level of mutual acceptance brings down a HUGE emotional barrier to their eventual reconciliation, and is a damn good development for agatha's show to conclude with.
toxic yuri soulmates who will always find their way back to each other as their shared love forces them to slowly let go of the beliefs that drive them apart and become less toxic brain go brrrrrrrrrr🤯