So it goes pretty much like this.MC starts hanging out with ML after chance encounter and due to some circumstances -?-he's been alive for a while now, walking the earth without agingfalls in loveturns out the 2 are soulmates and he was in love with her past selfbut back then the unaging one was MCthey keep repeating the process of death after meeting and leaving the other one to deal with an undying body that has an expiration date triggered by lovethis has been going on for centuriesthe reincarnated one never has memories of the pastthe undying one is always pining for their lost love and seeking deathML dies and MC bumps into his reincarnation 5mo2s

Also rmmbr - begins in a school setting I'm pretty sure
- ML had smn who knew his situation
- they bump into each other at a library? empty club room?
- ML is the grumpy tired of life angry at the past type
- MC is very animated in emotion

Now this is pretty old, like I read it bfr go even had the acc option tho I read it on a different site, and this was pretty much a plot twist so there was a fair amount of ch when they get closer and MC falls in love bfr the reveal and it isn't a oneshot, I just don't rmmbr it clearly bcs it's been such a long time and this is basically extremely memorable so it's the only thing that stuck. It's a BG but what the genres are I'm not even sure.

Omae ga Sekai o Kowashitai nara?

Thank you for replying but sadly, it's not that one. Tho I did already read that one in the past. The one I'm referring to is in a more shoujo like artstyle, that's why I said I can't rmmbr the genres clearly, that authors artstyle alone is enough to never be confused with a possible shoujo tag.
To retell it a bit more specifically than in the original post, ML met PLMC and fell in love with her, but she died feeling sorry bcs it meant he would take her place as a wandering unaging and undying person like she had been. Many years and MC and ML meet and he is now a closed off person with a harsh tongue, half resenting half understanding his past love but never able to forget. He doesn't act warmly to MC at all nor sees her as a substitute or smth. They bicker a lot but MC ends up falling for him dooming them to yet another repeat of the past. With ML dying and her becoming the wanderer destined to meet his reincarnation. The ending shows us that unlike the ML and PLMC who were both always looking at their original loves and tired of life or disliking people she'd still remained a cheerful person after years of being alone and finally walks past his reincarnation on a bridge? or a crowded walkway?

As I also said she has a very animated personality, loud emotions she doesn't hold back and that the story line I recounted is very much a plot twist we did not see coming, as it is shown in the later ch, and it doesn't start with showing bits of the past or even hinting there's something like this between them, just the knowledge that the ML is mysterious and there's a story about that, the MC is not really part of the intrigue in the beginning. What I retold is just the final outcome of the plot bcs I rlly don't rmmr the specifics of anything else.

*PLMC - past life MC

Replay?

~4400 manga completed
~1700 ongoing...

Fujimi Lovers? (nvm I read the second post, it's not this)

It sounds a bit like Primitive Boyfriend from what you’re describing of the end, but only bits of it are similar to your description lol

wine baths?

Thank you but it's not. That is a fairly recent manga what I'm talking about has been finished since the beginning of the 10s with the possibility of even earlier publishing. It's not isekai or another world, as I've said they met at a library or club room there is no time travel involved.

@tsiox
Thank you for replying anyway!

@Aremon
Thank you! But not what I'm searching for. Mine is a japanese manga, doesn't feature a student teacher relationship, nor is it love triangle focused. MC is not in a relationship with another. The ML's personality is not aloof or distant, but rather teasing prone. And it's not ML's never ending life of repeatedly chasing different incarnations of MC, but a cycle of reincarnations (A) falling in love with the person who was in love with them in their past life(B), than one dying when feelings are confirmed. That is, A and B keep switching places in the equation of dying and living on.