Except that the entire story of Ai no Kusabi is actually about Riki and not Iason. I haven't watched the films, so have no idea how they portray the situation or how much of the actual series of books they get through... but I would advise you to read the original books. It might be eye-opening.
I believe that the film is a much reduced version of the book. also in the movie is the story of Riki. but this comic is just a joke, I'm not saying Iason is the protagonist only because I'm comparing him to Hawke (who is a protagonist in the game) however, I can not read the book, in Italy you can not find it, and even in English can not find it. might be useful the book in digital form, so that I can get help in the translation from google translator. I unfortunately can not read well and enjoy reading a book in English. I make too much effort to follow the translation. in fact this is a pity, I've always wanted to read it.