Cute.
That's the only word Tatsuki would use to describe his cousin.
The way he pouted when he was pissed off or when he didn't get his way. Kotarou had always had a very childish face, so it was natural that he would look so cute most of the time.
Of course, Tatsuki would never admit this to Kotarou (or anyone else he planned to let live). He was supposed to be 'Mr. Stick-so-far-up-his-butt-that-he-couldn't-take-a-crap' (or so Kotarou liked to put it). But lately he hadn't been as bad as he use to.
In fact, he had actually answered a question from the short blonde with an actual word. The boy was so shocked that he just stood there gaping at his cousin for almost half a minute before finally walking away slowly.
The only reason Tatsuki was being nice in the first place was because the face Kotarou made when he was happy out-shone all the other faces he made. Sometimes he just couldn't help it. Even he had a small side of his brain that adored things cute.
But the one thing Tatsuki liked the most was a soft, gentle smile that only he ever saw. It was when Kotarou was truly happy that he was there. Like the many times Tatsuki had been there to save him when the blonde was kidnapped or in trouble.
So, if Tatsuki had to use one word, it would be cute.