Crosses the Line Twice: It veers at a non-euclidean angle to cross over an infinitude of lines that should not exist.
Crowning Moment of Heartwarming: Despite everything she's gone through, when Nana dies, she resurrects the dead kitten she spent her last few hours of life with and makes flowers bloom in the alley she died in. Doubles as a major Tear Jerker.
That tiny timeframe of happiness Nana has with Marcelo and Minami when they start paying more attention to her. They also never intended to abandon Nana. The plan was for Kurama to meet with Nana but Minami had faith that she would pick them over him. The ending also gets a little happier when one notices that the couple's shadows are seen as Nana dies.
Darkness-Induced Audience Apathy: A common criticism by detractors. Nana's life sucks so very much that it can be difficult to care about what happens when you know it isn't going to get better for her.
Nightmare Fuel: Combined with Tearjerker. Nana's world is the sort of existential nightmare where life has no meaning, there will never be a happy ending, and no matter how you hope, no matter what sort of happy ending you may beg for, there will only be pain. And cuteness, which only makes it worse.