User blog comment:B214/Talk About What You Want! 3/@comment-3965848-20150408202841/@comment-1359322-20150409085620

I'll just try to explain it more simply and accurately.
 * 1) Season 1 didn't have indication of split arcs.
 * 2) Season 2 had it in the logo.
 * 3) Season 3 didn't have indication of split arcs.
 * 4) The first 2 Volumes can also be said as the Red Dragon Emperor's Awakening arc.
 * 5) Episode 5 & 6 are fillers created to cover the gap of 12 episodes.

Hence the split arc writing is omitted from Season 1 because since TNK hasn't mentioned or outright show it like Season 2, saying it's split into 2 arcs is purely speculation, even if they did animate the first 2 volume.