Un:Birthday Song ~Ai wo Utau Shinigami~

Kanno Hotori was a normal girl leading a normal life. One day, out of the blue, two unfamiliar guys appear before her. The strangely-dressed guys informed her:

'You only have one month left to live'.

Calling themselves 'Reapers', they had come to inform Hotori that the end of her life was drawing near. Having to obey the fate that came upon her, she had to give the Reapers her soul. However, just before she did so, Hotori had a wish she wanted granted dearly.
That wish was to tell her one-sided crush that she loves him.