Nagisa dies giving birth, MC leaves their child with Nagisa's parents and becomes a drunkard. Few years pass and parents of Nagisa decide to leave MC and his daughter alone for awhile so they get to know each other. MC realizes his mistakes and decides to raise her properly. She falls ill with the same sickness that Nagisa has had all her life. She too then dies....BUT SIKE! Magic happens and time rewinds itself and both of them are alive again!! Even I don't know half the things that happened at the end there, but its a happy ending at least. From what I understood when Nagisa was young she almost died and her father in his desperation begged the spirit of the city to save her. Throughout the story it has been shown how the trees and stuff around the city are being cut down for various purposes and that probably meant the spirit was dying too. Nagisa was directly connected to the city that way and her daughter Ushio was too.
@DeOneChester@Walter_vi_Britannia Thanks guys, I'll probably check it out. I like stuff that can get me so invested in the characters that it makes me cry if they die or something happens to them. As long as it's not a sad ending with everybody left dead I'm fine