Spirit Circle by Satoshi Mizukami
Fuuta lives a pretty normal middle school life. He has good friends, occasionally sees ghosts near his house, and a birthmark he covers up but all of that is just normal. He's curious about the new, sharp-tongued transfer student Kouko but when he goes to make friends with her Fuuta realizes that she already knows about him. The two of them have been clashing across millennia, being reborn again and again after Fuuta once committed terrible sins, and it seems like this ancient conflict will finally end in this modern-day life.
I think that the largest difference between this series and Mizukami's only other English-translated work, Lucifer and the Biscuit Hammer, is that this series is much more consistent. I had a hard time getting into Biscuit Hammer because it has a lot of boring, low points early on and it takes a little while for that story to pull itself together cohesively. Spirit Circle is much more even-keeled and has a stronger sense of what it wants to accomplish (plotwise, thematically, and emotionally) from the start and stays on that course. This does mean that it lacks the soaring emotional highs of Biscuit Hammer, there's less contrast between these high and low points which I think is part of why they stood out less, but the good moments in Spirit Circle are so spread out that I could easily write a mini-essay on each of Fuuta and Kouko's past lives. Oh and the art is a bit better! I was never as bothered by the art in Biscuit Hammer as much as some people were, and it had some really well-framed, dramatic spreads, but the art really improves here and Mizukami seems to have a better idea of how things like anatomy (and eyebrows) work by the end.
Now, enough comparisons! Or at least Biscuit Hammer comparisons since I'd like to say that I do really like reincarnation stories but it's unusual for me to find a story that covers more than two of a character's incarnations and Spirit Circle goes for 8! The story also perfectly matches this set-up, by the time Fuuta has seen all of his past lives there isn't much legwork left for him to do as his middle school self, although there is still enough left for a big finale. I also appreciated how their story has a lot of similar beats each time but the execution is completely different in each go around. In some reincarnations the two feel compelled to kill each other on sight, in others they get along, even if even if fighting feels like "the more natural relationship for us." Each of the stories is rather short, the manga is shockingly short at only 45 chapters (and a tiny epilogue not on Crunchyroll), and it's a sign of how tightly paced the story is that these little vignettes all feel complete.
There are so many little details in how the story is handled that really made me love it, such as the fact that Fuuta and Kouko are not unique for reincarnating, they are "special" only because they have a way to remember. Everyone reincarnates, in fact I would bet that Fuuta and Kouko are on far beyond their eighth lives by now, and we see their classmates and family members time and time again which provided almost a comforting sort of grounding to the story. This was an early sign that in the end, yes Fuuta's former life Fortuna is a dangerous character but the world is wider than just these two characters, this is only one (admittedly long) story in all of humanity and most stories don't dare to keep the characters that "mundane". That idea is why I gravitate towards slice of life stories as well as plot-driven ones, I don't always want the leads to be the chosen, special few who will save the world, that concept is the unrealistic, suspense-breaking part for me and the fact that this story could be both a bit, save the world story and also be a smaller story about revenge forgiveness is more than I ever hope for.
The end of this story also reminded me of something I'd heard from other fans, Mizukami does have a bit of a multiverse going on and I'm sad that his only two translated works don't really interact with any of his other stories (there is a flowchart explaining all of this but I don't appear to have saved it). Usually after two stories I can say that I feel like I know a creator fairly well but here I feel like I barely know Mizukami at all! I can tell that he likes grand stories with complicated ideas of heroes and villains but these are pretty broad ideas! This story had a pretty satisfying, abet bittersweet, ending but it left me wanting even more of this kind of story and that might be a long time coming.