Boukansha no Koi

Overview

"I want to be by her side until the very last moment..." In the autumn of her twentieth year, Rachel marries her childhood friend Noah, her long-time crush. Even though she knows that the person Noah truly loved is his sister and Rachel's best friend, Alicia... Bright and beautiful Alicia was born with a heart condition, and her remaining time is limited. Rachel's marriage with Noah is built on on a lie, just to allow them to stay close to Alicia in what little time she had left. Rachel has moments of incredible happiness, but also feels guilt and heartache at the same time. However, before she knew it, she begins to notice Noah's passionate gaze looking her way… Who is the real "bystander" in this love triangle? The long-awaited manga adaptation of a heart-wrenching story of unrequited love, irreplaceable friendship, and mutual misunderstandings! (Source: J-Publishing, translated) Note: Includes three extra chapters.

Source: AniList