I'm predicting that they will both end up dying and being reborn again in the future. Ayafuji will actually die and Iris will go back to crysalis state only to meet again in the future and repeat the process all over again. They kinda hinted at it in the beginning here: https://dynasty-scans.com/chapters/vampire_chan_junior_chan_ch02#18 that Iris knew Sara before probably a century ago.
They also keep referencing those flowers that die and bloom over and over again so I don't think they're being that subtle of the direction they're taking it.
So in the end we'll probably get a bittersweet end where they'll separate now, but will always find their way to each other again when Iris wakes up.
(I'm not particularly happy if they do take it this way because i don't see reincarnation as a happy end. It always feels like a cheap way to bring couples back together, but they never have their old memories and are practically different people so even if they are "together" again, they arent really.)