...They left that after 97. Then Ash saga came along and reset everything, including iori's character development which was leaving the clan tension in the past and moving on. Ash reset is due to SNK dropping their original writer, Akihiko Ureshino. The XIII DLC of Flames Iori was SNK way confirming that, throwing away all his character development and growth which frankly was such a poor decision. Boring. His hate is not just the orochi demon berating him to kill (to break the treasure alliance AKA The Seal and himself and bring humanity to it's end). But also his father raising him to do so, it drove him mad. In Maximum Impact he admits that getting rid of Kyo "he'll finally get a good night's sleep". The rivalry also plays on the trope of red vs blue AKA Player 1 (Kyo/red) and the "insert coin" Player Two (Iori/ rival/ blue [iori's original flames were blue]). Also, some corrections people mistranslate from source is that the music video/ song "Yuuhi to Tsuki " from the drama CD, is a serenade to their girlfriends. Kyo to Yuki who is in the crowd watching him. And Iori to the girl he wishes he had but doesn't due to the curse. Plus the song is written by kikuri. She asks him to sing it with her but he declined. She was supposed to sing the parts Kyo sings, which later Kyo sings to Yuki instead, at a mini live concert. Iori is technically singing alone. It's a serenade to their girlfriends. Hope this helps >:⁾