Akaza is upper moon 3 while kokushibo is upper moon 1, they don't get along very well.. kokushibo is very quiet while akaza gets bothered by anything, Akaza gets angry at kokushibo because, he is upper moon 3 and akaza always wanted to become upper moon 1.

one night in the infinite castle akaza was very stressed with douma, the upper moon 2, while kokushibo was watching the fight from afar, so kokushibo is in his own room, Even akaza comes in

"Agh! Douma won't leave me alone!" Akaza says, very stressed.