Secrets and misunderstandings! But there's a valid reason for it, rather than them wanting to keep secrets for secrets sake? Who would've thunk it! It also feels like one of the better uses of a double reincarnation, rather than the standard (and often poorly handled) heroine/villainess reincarnation pair.
I like the chemistry of the pair where they're both trying to mess with the relationship based on their own knowledge. I think there's more than could be done with the concept, but it's reasonable for the scope of a one-shot.
1-2, 2-3, 2-4, 2-2, 2-1, 1-4, 3-2, 3-1, 2-6, 1-5, 1-3, 2-5, 1-1