Wait, now I'm more confused since rereading this. So who does Cale side with? Or does he n...

I didn't reread the manhwa recently but from what I understand Cale is ultimately on the side if his profit (?).
He wants his territory to be safe from the upcoming war(s?) so that he could slack of safely (a futile dream so far) so all his actions is to have the favor of the forces that could like harm him (directly or not) and protect himself from potential harm ( and others he care about but our guy is in deep denial)
Also I think the crown prince you mean is the one from Rowoon(not sure of the spelling) not the empire.
The empire is connected to the secret organization ( probably the organization is either created by the empire if I didn't misunderstand).
I apologize if I mixed up anything but I hope this helps ^^

cale side with rowoon kingdom since its his home. Rowoon is a kingdom… empire is mastermind behind the war. The north are trying to invade the south which is rowoon kingdom. Rowoon is more in the central in the map. Rowoon, empire the north and three other kingdom is on the western continent. SPOILER …There will be eastern continent as well in the later part

This might contain spoiler!!!

.
.
.
.
..
.
I guess you are not a novel reader so it's understandable that you got confused :)))
The Empire he refers to is reigned by crown prince Adin, the most wretchedest man there is. Cale plays a major role in creating an alliance between Rowoon, Breck, Whipper and the Jungle. Three northern kingdoms have formed an alliance as well called the Indomitable Alliance. This alliance is formed by Paerun, Akosan, Norland, Bear tribe and Flame dwarf tribe and they are secretly helped by Arm(Darkness). Those two alliances will clash in the war that is about to start early next year. And from there chaos will unleash(づ￣ ³￣)づ

I think you're confusing alver and adin, alver is rowoon's crown prince and cale's ally while adin is the imperial prince of mogoru and he's the enemy