I feel that this is a subtle and moving manga that repays several re-readings (and agreeing that the art is very attractive).
Yes; as it's a non-linear narrative, there's a lot of flipping back and forth involved! Yuu Morikawa is very skilled at imparting significance via a single panel (it happens in Mr. Villain's Day Off too).I can certainly see how it'd make that work if the central theme is about which brother is still alive, I'd hope there are hints threaded throughout that you could pick up on if you flip back through.