Blaine has been horribly injured in a hate crime, and is damaged. Severely. Kurt cares for him. It's awful and painful and hopeless and loving and hopeful and god damned romantic and good lord, I didn't read it when it first started popping up because I thought, "Brain damaged Blaine? Uh, no thanks."
I am happy to say that I'm a complete idiot. You don't even need to be in the fandom for this one. If you have ever been a caregiver, you're going to get it. If you've ever been cared for you're going to get it.
BRB, crying more. (All chapters are linked, thoughtfully so, and the time frame jumps around, but it DOESN'T MATTER. Srsly, not since The Boy Who Blocked His Own Shot have I sobbed over a story like this.)