Ok, here me out. Maybe the brother think he saw Akira before cos Akiras's dad's home burned and he had photos of Akira... And the shocking thing Kazuma's brother said its that the das is dead???
It should be somewhere in the beginning of the 4th arc, I think, so chapters 62-70. But I recommend to read the novel from the beginning, it's worth it
Honestly It was quite bland. The art is cute but the story is reeeeeally cliché, however, is a good read if all you want is to kill time.