Because you like Tyler Durden in Fight Club
Living with a curse, Kyo Sohma is sick of being treated like garbage his whole life. See them in Fruits Basket.
After several hundred years of shutting himself out from the rest of the world, Japan's not used to dealing with nations, See them in Axis Powers Hetalia.
The personification of America is all about superheroes, hamburgers, and spreading democracy and justice. See them in Axis Powers Hetalia.
With most of the people that Sango loved now gone, the only thing she wants is to kill the demon who destroyed her village. See them in Inuyasha.