Sorata travelled all the way from the shrine he grew up in to Tokyo to join the Ten no Ryu. He is the same age as Kishuu Arashi.
In the anime, Sorata seems to be portrayed as rather shallow, and seems more devoted to chasing after Arashi than to his foremost job of protecting the Kamui. It seems, for the first half of the film, that it would be totally impossible to care for this character. However this changes with the fight he and Arashi have with Fuma. This is where you suddenly realise his true devotion to not only his job, but the fullness of his adoration of Arashi. And here is also probably the first totally and utterly depressing part of the film.
Sorata is so sweet in the manga, it's no wonder so many people fall in love with him ^_^; He consistantly maintains a strong sense of humour, and his determined pursual of Arashi is both funny and touching. He knows his fate already, to the surprise of the others, and embraces it totally.
X Japan song:
'Say Anything'. I'm not sure if it's something in the song that reminds me of him, or if it's because the title 'Say Anything' has the same initials as 'Sorata Arisugawa', but it just seems to be a very Sora-ish song, and it almost seems to have a measure of his devotion of Arashi in it.