it's the fourth big event (corresponds to the 9th volume of the light novels)
would be the events that follow after those shown in the anime
If you follow the anime, the prequel arc is next. They skipped the summer vacation arc in the LN in-between the 9 school competition and Yokohama disturbance (you can see parts of the summer vacation arc in the newly uploaded first chapter of the double 7 arc manga). This follows after the prequel arc. The visitor Arc is the longest arc that has 3 vols in the LN. Double 7 arc follows next.
I'm confused. Is this one after, before or just a spin of. because if I am not mistaken
Mahouka Koukou No Rettousei - Kyuukousenhen. The one where they battle with the other schools inb the big event is the second one. So is this one the third then????????????