Right of Left is an integral part of SnF: Dead Aggressor. Without this, you won't understand why kids like Kazuki were kept secret from the truth of the island or their parents' real occupation. Without this, you won't understand why fighting a single Festum looked like doomsday whereas in the latter episodes of Dead Aggressor, it was almost a piece of cake. Without this, you won't understand why Soushi is the way he is. Much of what was unexplained in the beginning of Dead Aggressor is eventually answered in Right of Left. The tone is much more darker and depressing, which adds to the atmosphere ofdespair felt in the beginning of Dead Aggressor.

Absolutely do not skip this.