I'm trying to find this manga about an immortal woman who has already lived a long life thus she tries to commit suicide on a daily basis. She has someone who assists her to commit suicide: a young guy. The story started while he was strangling her to death while he is crying and saying something, I forgot what, probably don't leave or something cringey. But after she died she came back to life again and started getting mad at him because he's noisy like s child who lost someone but he became happy again like nothing happened after she told her to stop crying.
Anyway the ending was the girl having her body dismantled into a firework's powder then got shot and exploded to a lot of pieces which took her years to comeback to life again. She went back home and asked someone about the dude who used to assist her in committing suicide and the man who was asked said that he committed suicide because he lost his girlfriend and of course after knowing that the girl called him a dummy or something.