^Yukio was my first favorite, he actually was the reason why I started to read AnE, he looked so good in the color page with his glasses and a gun.
Then came the Kyoto arc and I decided that Yukio needs a psychiatrist like, immediately, and Rin might be doing some off-stage thinking and I like intelligent characters.
It was a different story for me... Rin was the one that made me see AnE, I decided from right on that he was my favorite... But I eventually love Yukio's character more..
Yukio for me is the most flawful and most real character in this series... If there is one character who I can say a unique fellow and who can walk among us, it is him! He probably is the most human-esque character in the sense that there is darkness and weakness in him, and to see how he struggles to overcome it is what makes his character beautiful for me...
At the same time, I find him the most tragic in the series. The boy had been seeing demons the moment he was born, and you could tell that this factor had cause so much psychological and emotional defects on his part. Yukio isn't a complete troubled child because he has a loving father and brother, but for a child to see scary creatures everyday, secretly undergoing exorcist training, just imagine how much stress that is for someone at a young age...
In the long run, we can see all of these factors manifested in him little by little in the manga. He had developed inferiority complex to his brother, somewhat even jealousy and rage, because of the unfairness of the situation which is not in his control. But at the same time, he had learned to hate himself as well... But we could see him struggling, trying to correct his ways in his own judgment...
Instead of a jerk, I could see being overprotected... Yes, his actions may had been harsh, but that is his way, and that is because he is smart and serious, and he always wanted to play safe when it comes to Rin, because he knows the consequences of recklessness... He love his brother so much, and sometimes he can be to extreme, but can you blame him for it?...
At the same time, he probably has the best character development in the series... At first I thought he will be this Tohru Honda kind of person, but surprise, surprise, homeboy is badass... His transformation from a crybaby to a notable genius exorcist is remarkable...
A hot stud with immense skill and power with psychotic tendencies? What's not to love?... Just imagine when he really went berserk in the future? Oh the beautiful tragedy...