Next up is that I don't believe Akira liked or loved Sekai at all, at least not by the time of the accident. The reason for this is that after the flashback, when Akira is talking to the ghost/god/delusion of Sekai, he seems not only cold but somewhat spiteful. We know Akira's feelings moved on based on the evidence of him eventually dating Nikki and whatever happened between him and Maya (if she existed in reality and isn'tan angel). If Akira wanted to move forward, but Sekai wouldn't let him (if she was even half as clingy as Ami appears to be, then she definitely would not let Akira go, so I believe that if he did cause the crash, it wasn't to get rid of his brother but to get rid of Sekai. Nikke even says that the wreck wasn't what caused the big disappearance and that he bounced back after a while. (I think, I'm dead tired right now, and I'm probably misremembering everything that happened in the update.)