Yes, the part where you get to invade the demon's main liars. Go on through and find a village on route. Once you're there, you'll be facing a strong foe. If you like to do damage on em, do spells, because that's the only way to hurt em at present, even with the overpowered gear that you can get in the debug room.
From that point on, the story is pretty linear. Side quests are kept to a minimum, with an expansion for one of the side quests (a temple totem for artifact quest in the mansion) and that's about it.
Quests wise, just do what the game wants you to do. I'm not spoiling anything, so let me skip a bit to where you can "control" where you're going to go.

After you're done there, you'll enter into "No Mans Land" or unintentional bug haven as it is the next big expansion since version 3, so expect bugs to appear.
You'll want to travel north until you see an igloo and a fort of some kind on a snowy island. You'll be able to continue the quest further there. There aren't any side quests, though there are hints for some in the future. Main quest wise, go into the clock-like structure, and finish what is going on there there. Note: keep an eye on the dialogue as since it's new, there is no "quest" even though it is one. It'll help to note when you're done, it'll let you leave the place. Go to the igloo, and finish the journey there. Also, prepare for a good few rounds of a fight. Approx 3 fights minimum (random encounters will increase that) and a boss fight will occur. You can back off, but it will take you a good 5 or so minutes before you get to a teleport wall, so be on your guard for that.