You start off on the snake way with 100z. You are told that you must see King Yemma, ruler of the underworld. Your path takes you to the end of the snake way where a plane, called "The Higher Plane", awaits you. It's docked at the end near King Yemma's Castle. Start off by going right until a dialogue box appears, telling you that you can double tap the 
to make your character run. Continue going right until you hit the end. You'll be at some stairs. Go up. At the top, you will notice what looks like a big wall, but is actually a desk. Also, some cloud-like things are floating around. These are the souls of dead people. There are two other people here, King Yemma's assistants. Walk up to the desk and push the 
button. Then proceed to the northwest, where a door is being blocked off by one of his assistants. Go up to him and talk to him by pressing the button. He will be shocked that you still have your human body, and will let you pass on through. You will now be in the docks where you will see two planes: a white one which leads to heaven, and a green one which leads to Grand Kai's planet. You can't take the white one, so your only choice is to take the green one.
When you arrive, the only way you can go is south, since the mansion is off limits at the moment. You will immediately see a save circle in front of you. Be sure to always use these. As soon as you enter the next area you will meet Olibu. He tells you to talk to the other trainers here to learn some useful information.