Melfina_chan

The original millennium earl disappeared and split into two children, Nea and Mana.

Mana slowly went insane and killed Nea because his mind kept telling him to kill him and become the one true Earl, he later went insane with grief and killed himself.

When a noah dies, they can revive later but their memories get damaged unless they find a host who can keep their memories safe until they revive in that host's body.

Nea knew Mana was gonna kill him so he found Allen who was a random soldier fighting in a war.

In exchange for being Nea's host, he gets to have a free wish.

The bookman clan is tasked with recording the history of the whole holy war and there can be only one bookman at a time.

Beta Lavi was supposed to inherit the bookman title but he got so fascinated by Nea, he abandoned his post and found Allen who was his host.

They traveled together for a while until Apocryphos (the guardian angel for innocence) attacked them.

He tried to make the helix of life consume Allen but Lavi jumped in to save him.

Allen was chosen by the innocence in this fight because it's drawn to people with tragic fates, he also slowly got consumed & reverted back to his childhood form

Lavi gets consumed by the helix and Allen is thrown out after 8 years of standstill.

Since there can be only one Lavi, once the beta one dies a new Lavi (our version) is born.

At this point, Mana gets revived but since he didn't have a host his memories got damaged & doesn't remember why he lost Nea (he doesn't remember killing Nea)

He joined the circus because he was hoping that Nea would come to see the show like everyone else does and reunites with Mana.

Apo erases all of freshly shrunken Allen's memories and sells him to a circus (not sure about this part but I think he was hoping that Allen & Mana would meet one day and Allen would kill him)

And exactly that happens, Apo manipulates a jealous performer in the circus to kill Mana's dog Allen (Mana probably remembered that name from his previous life but didn't realize it)

MC who's currently nameless, gets enraged and tries to attack the dog killer and unconsciously activates his innocence

Mana tries to stop him but Allen accidentally injures him which wakes up his inner Noah and becomes the Earl again.

After that, Mana becomes the Earl, kills everyone in the circus and completely goes insane after being calmed down by Cross.

He forgets everything and thinks MC is his dog Allen, MC doesn't correct him and they live together for a while until Mana dies in his sleep one day.

I'm not sure about the next part but Earl offers to bring Mana back and Allen accepts it, I'm kind of confused about this part because if Mana is the Earl then who are they reviving?

Whatever ''Mana'' curses MC and a little bit of his soul becomes Allen's cursed eye, he later kills Akuma Mana with his self activated innocence

Previous Lavi's soul finds Allen and becomes a part of him, turning Allen's hair white.

After that Cross finds him and makes him his student yada yada you know the rest.

Currently, Kanda & general Tiedoll are working together to see what happened to Mana's corpse (they found the coffin empty)

Allen & Johnny & Link are at the bookman mansion, trying to find out what happened in the past.

The short hair girl you see in the latest chapter gave Allen a poison that can show him his past before Apo remade him because they wanted to learn what happened to the old Lavi who abandoned his job for Allen.

Thank you for the effort! I finally understood!