The outer wall is the means of access to the Plantation, the step before the doctor. Unlike other maps, gravity pushes items to the left rather than downward.
The booster V2.0 allows you to speed through the map without too much difficulty, otherwise, you will have to climb the wall slowly.
Below the exit from the Egg Corridor, you can find a small dwelling. You need Booster V2.0 or level 3 machine gun (which lets you 'fly' by shooting down) to safely enter, as it is extremely difficult to fly in and out with Booster V0.8.
This dwelling contains a few tiny people. The wife is looking for her husband who can be found in the graveyard (lower floor, might be hard to find). When you retrieve the tiny person and bring him home, you can optionally trade the Blade for the Nemesis. You can trade it back if you prefer the Blade, but the Nemesis is a more powerful item because of its improved range and firing rate.
Climbing the Wall
To proceed, you can climb the wall on the left side and proceed all the way to the top. There are several Night Spirits and Hoppers along the wall. About a screen up from the Dragon is a room containing the Nikumaru Counter. About halfway up will be a balcony you must go around. Near the top, there will be platforms with sand and Sandcrocs around them. At the top there will be a door that takes you to a room next to the Plantation.
If you have the Booster v2.0 and saved Curly, then you can collect the 290Counter in the room labeled with clocks. Otherwise, a mysterious force keeps the chest closed.
The counter allows you to unlock a new theme song for completing the final area within six minutes.
Entering the Building
When you reach the top and enter, you will see a scared Mimiga. Talk to him and he will reveal identify himself as Itoh. Talk to him and head into the Plantation.