After Kyubi tricks you into defeating Massiface for him at the construction site, you plan on visiting Eddie's house in Breezy Hills.
Let's Go to Eddie's!
If you go to Breezy Hills, you'll discover that you can't get into Eddie's house without a Rank B Watch! You will have to go to Timers & More if you haven't upgraded your watch. Talk to Mr. Goodsight and start the Rank B Challenge.
Rank B Challenge
There is a Tengloom in the Construction Site in Downtown Springdale (the building that you went through before you fought Massiface), there is a Flumpy in the Shopping Street Narrows (an alleyway in Flower Road of Shopper's Row) and Mad Mountain in the Abandoned Tunnel.
The Mad Mountain is more difficult to find than the others. You have to follow the path behind the Shrine in Mt. Wildwood, northwest of Catfish Pond (where you found Bear's Mom's ring). The path leads to Abandoned Tunnel West.
In the Abandoned Tunnel, there is a broken mine cart near the entrance, and there is a working mine cart to the right. Get into that mine cart, then go west, then clockwise to cross a wooden bridge. You should see a Rank C Lock nearby. You don't have to go through it, but there are some tougher Yo-kai that you might want to befriend.
Go south from the Rank C Lock and get into the mine cart there. You'll reach a treasure chest. Go back into the mine cart, then go to the northwest of this area and you will find a switch. Use it to switch the tracks, then go back to the mine cart that you just used.
Go northeast from the mine cart and you will find a Leadoni blocking the way. After you battle it, you'll get the Leadoni Wheel. Go north of there to find the Mad Mountain that you need to defeat for the Rank B Challenge.
Go back to Mr. Goodsight to complete the Rank B Challenge, then go east to Uptown Springdale, and from there go east to Breezy Hills. Go to the northeast of the area to find Eddie's house. Use your newly upgraded watch to open the Rank B Lock and go into Eddie's house.
Eddie's Mom will greet you at the door. Go upstairs and talk to Eddie. He invites you to go to the museum with him. He has to do chores first, so he says that he will meet you at the museum.
To Gourd Pond Museum!
The museum is southeast of Eddie's House. Go inside and go to the right to find Eddie. Talk to him and you'll discuss the T. rex exhibit. Next, go up the northern stairs and go to the upper-left of this area to find Eddie again. Talk to him and you'll discuss another exhibit. Then go to the bottom-right of this area to find Eddie again. You'll discuss the strange artwork. Then go downstairs and talk to Eddie near the front desk.
Eddie says that he heard a rumor of an exhibit in the museum that was moving around on its own, but he couldn't find it. Then you overhear the receptionists discussing a suit of armor that was supposedly moving around on its own. Eddie wants to check it out at night, so go home and sleep until night, then come back to the museum. Eddie will be outside, so talk to him.
He says that since the front doors are locked, you have to look around for another entrance. Go around to the east side of the building and check on the weird mirror. Before you can use your Yo-kai Watch on it, Eddie shows up. Then the mirror flashes and transports you into the museum. Whisper says that it was a Yo-kai called Mirapo.
Eddie wanders off, then the Mirapo appears and says that it needs help stopping the armor that walks around at night. Eddie comes back and says that the suit of armor must be in the vault with the undisplayed exhibits. Eddie will try to disable the museum security system while you look for the key to the vault. Mirapo can teleport you to different areas of the museum, or outside.
Find the Vault Key
There are Yo-kai in the museum that might jump out and attack you while you walk around. There is an Eyepo southwest of the reception desk.
Talk to the Mirapo that is to the southeast of the reception desk. It will warp you to the left side of the area. Talk to the upper Mirapo to be warped to the second floor. Go toward the left and talk to the Mirapo there to be warped to the far right of the first floor.
Go to the northwest of the dinosaur room to find another Mirapo. It warps you to the middle of the first floor. Approach the stairs and Eddie will disable the security barrier so you can go up the stairs. There are some treasures here on the first floor that you can reach now that some of the barriers are gone, so go around and get those if you want. Then go up the stairs.
There is a treasure to the left. After you get it, go to the right of the stairs and talk to the Mirapo to warp to the right side of this floor.
Talk to the spinning Mirapo to go to the area in the bottom-right where you can get a treasure. Then talk to the Mirapo to go back, and talk to the Mirapo in the bottom part of the room. Go south from there and check on the plant to find the vault key.
Talk to the Mirapos to go back to the stairs, then go down and talk to Eddie at the reception desk. He disables the rest of the security barriers.
The Armor in the Vault
You might want to talk to Eyepo to heal and save. Then go to the door that was blocked by two lasers, and open it. Go to the back of the room and check on the mysterious armor. It suddenly turns into the Yo-kai Phantasmurai and attacks! Sometimes the front of the armor breaks and a mouse pops out. Be sure to target the mouse when this happens.
The Armor's True Face?!
After you defeat the Yo-kai, the mouse runs out of the armor, so Eddie thinks that the armor was only moving because of the mouse.
You go out and tell Mirapo that the mouse is gone and the armor won't move anymore. Mirapo befriends you. From now on, Mirapo can be found in various places and can warp you to other places. Just be sure to talk to Mirapo as soon as you see them, because you have to activate them before you can use them.
This ends the chapter. Next is The Extreme Dare.