Kimi wa Tsukiyo ni Hikarikagayaku

Ever since the death of someone important to me, I've been living recklessly. After I became a high school student, there was a girl in my class who remained hospitalized due to "luminescence disease." This disease is named for the fact that the bodies of those who suffer from it glow faintly when exposed to moonlight, and that glow becomes stronger as their time of death draws closer. The girl's name is Mamizu Watarase.

After learning that she doesn't have long to live, and there are things that she wants to do before she dies...

"Will you let me help you with that?"

"Really?"

As this promise was made, the time that had frozen for me began moving again.

(Source: Kadokawa, translated)