Title: Death Becomes Her
Summary: She watches, and when the time comes, she makes sure that none of them are alone – because, really, that's all she can do. Celty-centric.
Looking back, she realized, her whole life was simply death. She lived for death: death was her job, her employer, and her scythe, her bucket of blood, was simply the messenger. She should never have allowed herself to become close to those humans, because she knew how short their lives were – like mere seconds compared to hers.
Mairu was the first to go, much to everyone's shock. She makes it to sixteen before the doctors tell her she has cancer. She doesn't let it get to her, determined to make the best of the time she's got left. She spends as much time as possible with her family, and, for her birthday, Izaya goes to Shizuo and asks him to introduce her and her sister to Kasuka. He agrees, out of pity, but she doesn't let it get to her. She meets Yuuhei, graciously thanks him for coming to visit, and dies a month later with a smile on her face. Izaya is holding her hand for the last six hours of her life. There's a funeral, and they all go, but nobody really cries. They miss her, and they all cared for her, but Izaya isn't sure how to feel, Aoba doesn't know what he feels, and Kururi can feel Mairu's soul. They've become one again, she claims.
Kururi is next, followed shortly by Aoba. Izumii breaks out of jail and comes after them, killing them both while they're making love for the first time. An enraged Izaya comes after him with a gun, shooting him six times – four in the chest, once in the nuts, and once in the head. He has a mental breakdown soon after and disappears for a while, but he comes back soon enough. He's changed, though, and something isn't right. Namie is the first to notice, seeing him talking to people who aren't there. He's talked to himself before, but this time he seems to be able to see whoever he's talking to. She calls Shinra once she hears him call one of them 'Mairu'.
After Izaya disappears (this time, he's in the hospital, and he's probably being diagnosed with schizophrenia), Shiki makes an enemy out of some company, and they come after him. He gets away with a bullet in his arm, and goes to Shinra for medical aid. It doesn't take long for Shiki's enemies to go after Shinra, and Celty comes home on the third anniversary of their marriage to find him on the floor, a bullet through his skull. She doesn't go after the man – she doesn't have to. Izaya finds out, leaves the hospital he's in, and strangles the killer to death right in front of her, though she doubts he even knew she was there, before laughing like a maniac, taking a gun, and blowing his own brains out.
Shizuo goes next, but he takes nearly thirty years before following his mortal enemy to whatever afterlife there is (Celty is sure that, somehow, no matter where they end up, they'll be fighting when she next sees them). He marries Vorona, they have kids (two, she thinks, but a third is on the way), and then the past catches up to the Russian woman and Shizuo dies defending her from her attacker. At his funeral, Vorona tells her children not to cry, claiming that this was proof that their father was a brave and honorable man, and that they should have been proud to be his children. They are, she's sure, but all of them – and Vorona, too – cry anyway.
Mika and Seiji disappear at some point, having eloped, and they live happily together – until Seiji realizes that he's fallen for her, meaning that he's betrayed Celty, meaning that they both have to die. Mika agrees with him, as she always does, and the two run each other through while smiling and proclaiming their love, in some kind of murder-suicide gone horribly right.
Namie finds them, in Korea, smiling into each other's corpses. Nobody's bothered to move the bodies, so Mika's left eye has fallen out of her skull, and Seiji's ear has rotted off. Namie kills herself right then and there.
Mikado, Anri, Masaomi, and Saki live together for a while – and Celty isn't sure who's sleeping with who; they're probably all together – until Horada breaks out of prison and kills Mikado, Masaomi, and Saki. Anri slays him in a fit of revenge, and then comes back to Ikebukuro. She's in her fifties now, Celty realizes, and has grown quite a bit. They hug, and Anri takes up Izaya's old job – providing people with information. She isn't as good as he was, and she knows it, but she's able to find jobs for Celty, and do her best to make sure that nobody kills anybody else.
Rio goes next, in a car accident ten years after Anri's return. Both Anri and Celty go to the funeral, even though neither of them knew her well. And the rest go from old age – Anri is eighty-seven when she dies in her sleep, Vorona at ninety-six, and Celty loses track of Vorona's children at some point. She never really got to know them, though, even though she's the godmother of two of them.
And then, she leaves. Izaya had had Namie send her head to her after he'd been hospitalized, but everyone who had known Mika already knew what she looked like. Shooter leaves his motorcycle form, Celty changes her biker outfit to the outfit she had before she lost her memories. She does not stop by their graves, and she does not say goodbye to everyone. The city watches her leave, some of them crying, a couple people wave goodbye, but she does not look back.
After all, they're waiting for her. Shinra snatches her head and kisses her, Shizuo and Izaya take a break from trying to kill each other (even though they're already dead) and try to, respectively, kill Shinra and save him. Anri, Masaomi, Saki, and Mikado, all looking the way they did when she first met them, grin and wave, while Mika and Seiji kiss each other nearby. Namie watches for a moment, before smiling and nodding at her. The twins tackle Izaya to the ground, and Aoba makes comments implying a taunting sort of jealousy, and Namie laughs at the irony of Izaya being the one accused of incest for a change. He denies it, looking horrified, and Celty turns to see Kasuka and Ruri, and wonders when they died. It doesn't matter, though.
Now, they have eternity.