Three Days of Happiness by Sugaru Miaki

Translated from Japanese Completed Romance Supernatural

It seems that there's not going to be a single good thing in my life. And that's why the "assessed value" of my lifespan was a mere 10,000 yen per year. Disappointed by my future, I sold off most of my lifespan and became desperate to attain some happiness in my short remaining time. But everything I did just seemed to backfire. Meanwhile, the "observer" Miyagi watched my fruitless attempts. By the time I noticed I would be happiest living for her sake, I had less than 2 months left to live.

And, in the end,
the love you take is equal to the love you make.

- The End
The Beatles

1: Three Days of Happiness