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After the conversation in which you tell your story and everything, you find that Pichu is missing.
Soon you start your first Mission.
Get out of the house and go north. You can save and recharge at the machines kept there. Then go west for some time and a man will run to you and warn you. Now enter the forest.
Most of the Pokémon around here are scared by the commotion so you will have to chase them as they will run when they see you. Go north and you see the Pinchers again, catching a Pokémon. Then you see the Poké Assist tutorial. After the tutorial, follow the path west when you get to the place where Spinarak fall on you. Catch a Pokémon with Cut 1 To cut the small log. Hoothoot is the nearest but if you have a Wingull it can also help. Then go north and you see the Pinchers trying to pinch Ukulele Pichu, that is until Ralph interferes. They order Buizel and Croagunk to attack you. This is your first group capture, so just focus on one first then go for the other one. After the capture Pichu runs off into the cave. There is a save machine there, so save if you want and get in the cave. Also there is a Pachirisu there, it can recharge your styler.
Follow the path north, catch a Koffing and then go east. Use Koffing to push the Round Rock down. Now follow the path and jump down from the ledge. Then you catch up with Arley, the person you are searching for. You find that he is okay. Then Pichu goes in deeper. You might notice a stone depicting Drapion, it will open up later. For now Follow Pichu.
You see pinchers doing something. Then Pichu comes in and tries to shock the pinchers, but ends up getting its ukulele broken. You come in and immediately get to capture Cranidos. Catch it and the pinchers fly off. As they fly off Raikou appears and chases them away. And that is a Mission Clear and you get 50 ranger points. Go east and don't mind the locked door for now. Go south and then west. Enter the room on the west and catch that Cranidos, then exit the cave with the other exit. If you use a Tackle 1 on the tree there a Murkrow will fall down. Break that rock on the west with Cranidos. Exit the forest.
Back in Cocona Village
Now go back to Booker's house. If you have Zubat you can cut the fence to go through a shortcut. There will be conversation in which you will meet Edward. Continue on your way to Booker's house.