Author links:
https://x.com/Machinehead2019
https://machinehead21.newgrounds.com
https://naughtymachinima.com/user/machinehead

The right chronology would be:
The 13th Grimm III{Vol. 1 > Vol. 2 [W.I.P.] > Vol. 3 [N.R.Y.]}
The 13th Grimm II{Ep. 1 [video]}
The 13th Grimm IV{Ep. 1 [video] > Trivia > Ep. 2 [video]}
The 13th Grimm V{The Masqueradeball}
The 13th Grimm VI{Season 1 > Season 2 > Season 3 > Season 4} (you are here)
The 13th Grimm I{Chapter One}
The 13th Grimm VII{[N.R.Y.]}