The number one rule of the mountain pass is this: You must not be seen.
There's a ceremony going in in Kibombo up ahead and they've closed this pass off for everyone. If you're spotted on your way through, you're escorted back to the start, even though the three of you could probably take out a load of tribal soldiers. Anyway, to start, head north to trigger a scene. Once they've finished their little talk, head right past the torches and shove the boxes up ahead so you can climb the vine and hop across. Head up the vine and across the archway. On this side, shove the pillar off, and head north up the vines. Up here, use the box to hide from the patrolling soldier. Push it along until you can climb the vines. Do NOT climb down the next set of vines - the solider will find you. Instead, slide down the groove to the right of the crate. Walk around to the right above the solider and get the Disk Axe from the chest (equip this on Felix, but don't sell your Storm Brand, since you'll want to give it to Piers when he joins your party). Now, use the box back on the left to hide yourself from the solider until you're far enough left to use the vines. Back up here, use Lash on the rope to get over to the other side, then head south. Shove the viney pillar into its groove, then head all the way back north and through to the next area.
Don't climb down the vines - instead, move the large box so that it's one square away from the edge. Wait until the guard stops below, and shove the box off to trap him for a humerous effect. Climb down the vines and walk over to the chest to get some Power Bread. Use it on whoever has the least HP (most likely Sheba). The next part involves walking past the dog and if it sees you, it'll alert the guards of your presence. There are two ways of getting past it:
The quickest way is to use 'Tremor' on the box with the bone on top of it so it falls and the dog will be too distracted to notice you. The longer way is to walk left to the viney stump and climb up it. Hop across to the section with the pillar. If you want the chest, you can shove the pillar off so the dog gets trapped north of the pillar. Hop across and climb down the vines to reach a Tear Stone in the chest. This is the first forgeable material you get, but you can't do anything with it for a while. If you do this, you'll be forced to leave the area to the south, then come back to reset the pillar. Trap the guard with the box again, then when it comes to the dog, trap it in the area where the Tear Stone chest was (this is somewhat harder than before - if you fail, leave the area to the south again, and try again). Hop back to the left when you have and climb down the vine pillar. Hug the rock the pillar was on as you go right, because if you don't the guard to the north will spot you, and it's back to the start. Enter the cave directly ahead and inspect the middle crate to get a Smoke Bomb.
When you exit back outside, you'll notice the dog has been freed. You can't sneak past it, so this time, use Tremor to knock the bone on the crate to the ground. This will distract the dog. Go around to the right and clear the ivy with Whirlwind. Go through the cave, then back outside go all the way to the left, past the soldier. Climb down the vines and descend the stairs to the south. The Jupiter Djinni here is inaccessible for the mean time, so just head across the river and out to the world map using the exit to the west. On the world map, cross the bridge and head north to Kibombo.