Shinigami no Hanayome: Yomei 7-nichi kara no Koufuku

Overview

"You’re gonna die in seven days." Most people would break down in tears upon hearing such words from the Grim Reaper himself. But when Aibi, a terminally ill teenager, is given her fate, she simply smiles, thanks him for the warning, and even calls him kind—leaving the Reaper utterly baffled. No one acknowledged their existence until they found each other in this story about a love that blooms beyond death. (Source: Manga UP!)

Source: AniList