Aidou by Hanabusa Aidou.

3 months had passed. I wasn't satisfied at all! That little spoiled brat, fluttering around Kaname-sama all the time. Just what did she do to deserve his attention like this?
It had me wondered, seriously...
So I kept my eyes on her for a while, seeing what would happen.
Yuuki Cross wasn't special. She wasn't pretty. Didn't have an all amazing character. She could even be quite mean.
But as time passed, I noticed everyone in the house was smiling. And among them was Kaname-sama, of whom I had thought I would never see him smile sincerely.
She made him honestly happy. And to know that someone doesn't need to be special to make another happy gives me courage.
I guess... I wouldn't mind sharing Kaname-sama with this little brat for a while.

"You're so self centered." Ruka noted.
"Well I'm sorry! I pored all my feelings in this little piece, you know?"
"Which is quite stupid, knowing you have to do another 7 of them." Akatsuki sighed.
Yuuki giggled. Aidou was such a weirdo... but well, since they had been together for a while already, she knew how rarely nice the words Aidou had written had been.