He was too young to remember the first time he shifted.
He's had his fair share of children books that described mermaids, all with colorful tails and mostly beautiful women with alluring voices, but he has never heard of a young boy, much less a young boy with a white tail since they - the mermaids and mermen - were often depicted so colorfully and beautifully in stories that the sight of his own tail made him feel somewhat disappointed in himself. But no matter, he had told himself then, it was fine. It wasn't like color was everything.
As it turns out, however, color was everything.
His mother told him that the color of their tails symbolized their aptitude, their strengths and their abilities. It was their identity. Each shade has its own meaning and that's why mermaids and mermen treasured the colors of their tails first, their voices and their scales second.
That was when he realized that it certainly didn't seem right that his tail was a blank slate. His mother herself had admitted that it was her first time seeing such a pale shade of white on someone's tail, and that the implications of such a condition worried her.
Again, he had shrugged it off, more to reassure himself that he wasn't as bothered as he seemed, but he was. It wasn't like he was willing to flaunt the fact that he had a tail around. It was his and his mother's secret, and he was fine. Weirded out, but fine.
There were worse things out there. At the very least, he wasn't a shape-shifting chihuahua.
So color wasn't a big deal. But it kind of was, and Tsuna is a bad liar.
