After a nice intro cutscene you'll find yourself in a cave promptly named 'Start Point'. The Heart Canister will refill your health, the Floppy Disk will save your game (no Autosaves!) and the door is the way out. Press down to interact.
Once out, go to the left and continue down, we can't go right yet. Be sure to jump over the blood-covered spikes though, you only have 3 health, and these spikes will one-hit you.
At the point in which the cave curves around underneath itself, grab the item in the corner. It'll increase your max health!
This water will weaken your jumps, so jump from the edge to make this gap. Also be careful not to stay in the water too long, you do drown.
Contrary to instincts, you should climb into this Tiger statue's mouth, it's actually a door.
It's some dude's home. Loot his treasure chest while he sleeps to get your first gun, the Polar Star! Then make your way back around to where you began.
All those bats you've skillfully dodged better look out, as now you can shoot them down. Kill an enemy and it'll drop yellow triangles which level up the gun you wield when picking them up. Collecting enough will increase the level of your gun, but be careful, getting hit will make you lose some experience from your active gun!
You can also shoot your way through the blocks that blocked you previous. The door at the end is a Mimic, do be sure to shoot it before trying to enter it.
You'll fall into the Mimiga village, interrupting something. There's a save room on the right, but head left into the reservoir to progress.
Go to the end and jump into the water, interact with the sparkles to get an item, and quickly make your way out before you drown. Also, don't kill that fish, you'll thank me for it later.
Toroko will be there when you get back, but will run off again. Chase her down into the house at the bottom right of the village, or explore a bit to get the Map System just above it.
Inside the shack Toroko will attempt to "attack" you, send a single shot her way and she'll trip, allowing you to explain the situation. But you'll soon be cut short by two minions of the Doctor.
Misery will make off with Toroko, and you'll be left with Balrog who asks if you planned on trying to fight him. Say yes, and he'll start trying to charge and jump at you. Dodge his patterns and he's extremely easy. Or you could say no, and he'd just leave.
Head up to the top right of the villager and inform the Mimiga there that Toroko has been kidnapped, and he'll leave his post. Head inside the cemetery.
Up the top on Arthur's gravestone you'll find a key to the house at the bottom left of the village. Take it and go there.
Interact with the computer to enable the teleporter, and then take it to the Egg Corridor.
The Egg Corridor starts off easy, make your way forward through some jumping bean things and a few charging elephants.
You'll quickly find the Sue everyone has been talking about as she gets kidnapped by from Monster Mimiga.
When you reach it, go into the underground tunnel and up into Egg number 6, you'll find an ID card you need. Don't let that white thing touch you though, it's an Insta-kill.
Enter the room not far from Egg 6 to not only find out that you were indeed supposed to find the ID card there, but also get the Rocket Launcher!
Then go into Egg 1 and use the ID card you grabbed earlier to turn off the Shield you barely got to see.
Make it to the end of the Corridor to battle Igor who is protecting the eggs for the Doctor. At first he attempts to through weak punches, but soon starts charging up projectile attacks past half health.
In the first door afterwards you'll find Sue as she tries and fails to open Egg No 0 to escape on a Dragon. She'll reluctantly invite you to escape with her, and for now you should head back to the village.
When you arrive back, Sue is caged up by the villagers because the Doctor's henchmen took Toroko instead of Sue. Talk to her and she'll send you in her place to the Grasstown for her Brother.