Oh wow. I can't believe I actually stumbled upon this again. I love an obsessed top, also the twist that the big bro loves him as well was nice. It's like he was egging him on to do it. The last scene were he said "It's you who can't live without me" was a full circle moment since the lil bro keeps repeating that his big brother can't live without him. It was him all along. I can't believe I actually found this again, the tag I used were : yaoi, smut and oneshot. There were only three pages luckily.
Bakadane, Shitteruyo.