I'm not sure if its a oneshot or not but i think i'm quite sure, but here is how the story began:

The blond haired seme was walking outside then someone ran out of the buildin and bumped in to him. They fell and the "blue/dark" curly haired uke was apologizing and told his sister to apologize too 'cause it was her fault that he ran out of the building to accidentally bump in to someone. The uke complained how ugly his hair was and swore to shave his head but then the seme said it would be a pity 'cause the uke's hair was so beautiful then the seme's head began bleeding xD (i think beause he hit his head when he fell)

Soo does it ring a bell for anyone? Please tell me if you remember/know this story ^^

is it taikutsu wa warawanai

That's it! That's the one, Thank you ^^