Great Fang is simply a hallway leading to a strange corridor beyond. When Parin enters, she'll find Pino hanging suspended in a cage from some chains. Before you can save her, Tokaron attacks. You must defeat him.
Boss Battle: Tokaron
During the first wave of Tokaron's attacks, you can't really hurt him. Just try to avoid his attacks with dash guard moves to either side and don't fall off the ledge. You can hang from the edge if you like--which sometimes makes it easier to avoid the dragon flames--but that's it. When you've survived for a little while, Pino will shout that there are cannons in the area you should be able to use to defeat the dragon. Parin complains that she's too busy dodging attacks, which is when Motoro appears on a ledge below and starts firing cannon shots. He'll buy you some time, he says.
Now the action resumes as the ledge you're riding continues its whirling ascent. During this second phase, you must continue avoiding attacks from the dragon. It likes to send lightning bolts down on you from above at this juncture. The dash guard move will allow you to dance around them, but also watch when he sends two glowing orbs toward you. Electricity will arc between them momentarily, so make sure you're not standing in the way. After you dodge this series of attacks long enough, another cannon shot will hit the dragon. It will duck out of sight for a moment, then return to view again. This time, it's blue in color.
Now you just have to dodge some ice attacks. Even if you're struck, the ice attacks won't damage you much. Just use dash guard attacks and in a moment, someone will intervene in the battle. The dragon will take another hit, then collapse toward the ground. This particular battle is over.
The dragon lies in a heap on the cavern floor. All of your monster friends join you to celebrate, but it seems the celebration was premature. The monster lifts its head, then inhales all your pals. It rises to its feet to battle you and begins to change form until much of its body is covered in protective armor. Now the real battle has begun...
Boss Battle: Armored Tokaron
This battle is definitely a tough one, so hopefully you didn't lose too much life in the previous round. Tokaron has a lot of armor that protects him from your attacks as he prances around the arena. What you want to do is use drill attacks to chip away at that armor. That gives you more ways to hurt him, since his vulnerable head isn't always down within range.
Basically, Tokaron will use multiple attacks that do pretty severe damage if they manage to strike you. The green laser beams are a big deal. However, they seem to follow you anywhere that gets you close enough to damage Tokaron, so you might as well aim for his chest and head. If you keep your flurry of attacks fast and furious, his life meter will drain at a fairly steady rate and you'll win before he can recover from the damage you've done to his armor.
With that said, maintaining that pace can be difficult, and eventually the beast will regenerate his armor. After a while of taking damage because you've drilled away his armor, Tokaron will fly into the sky and you'll see the design of a pentagram traced across the ground. Make sure you're between the edges of the star, which will shortly begin to turn in a slow circle. Keep away from the glowing lines, which can harm you. The attack lasts only a moment before Tokaron finally discontinues it. By then, he'll have recreated his armor. Then it's time to strip it away and keep repeating the tactics that worked for you before.
This battle can last a long time if you're not ferocious and quick to take advantage of the moments Tokaron is at his weakest. If you maintain a steady offensive, though, you probably won't go through even half your supply of goodies. Then the battle is over and Tokaron is defeated. Congratulations!
And that's it. You've beat the game at last. Now you get to enjoy the ending. Talk to the monsters in Monster Village, then talk to Motoro at his gym. You'll learn a few things you probably already knew and then it'll be time to return to Monster Village because something is happening. When you arrive--which you do automatically--you'll see that Parin has reason to leave the village, and quickly. Once she passes through the portal, the game's credits roll. But is the adventure really over? No, it is not!
Now you can play through again on a new difficulty level (assuming you played on 'Normal' the first time through). There's a new sub-quest and there are more outfits to obtain. You start with the option to change into a nice set of Pajamas if you wish it, and you get to keep your stats (but not HP increases) as you start this next trip through the game. You'll even retain your wallet full of gold and any junk you had in your inventory when you beat Tokaron. Enjoy!