It's 'Goodbye' in English [Nagisa Shiota/OC] -- DISCONTINUED.

[AU Set in a World War]
The war's supposed to be ending but something had gone terribly wrong and it went on and on restlessly. They all thought they could win. And yet in the midst of it all, the bombs fell.
Nagisa Shiota, who's supposed to drove an enemy force out of the Kunugigaoka's perimeter got caught in the explosion and had been buried, with only the broken debris supporting him from getting fully swallowed by earth.
He thought that he'd have to die alone, but it looked like war's never easy to get out of even in death.