Walkthrough: Nino Island

Nino Island is a tall tower rising out of the ocean with multiple docks, and cities in the interior of the tower. The Nino Ruins, where the second key to the Mother Lode is said to rest, is also where Professor Barrel found MegaMan as a baby. However, you won't be getting inside them any time soon; the island's guildmaster has closed them off until the attacking pirates give up.

As soon as you near Nino Island, you'll be shot down, having been mistaken for pirates. Looks like you won't be leaving for a while...
Once inside the island, you'll be able to find Roll and Data near the #3 dock. Roll has brought everything you need to develop new weapons, so be glad for that.
Take the nearby elevator down to Ruminoa City.
Check the trash can here for 3,000 zenny.
Feel free to explore the city now, as there's not a whole lot going on. I do suggest you go through the blue door though.
There'll be a girl inside here that's hoping to get a pet. Keep her in mind.
Also, go through the door with the red bulb on the front to find the General Store (the door marked with a cog leads to the Junk Shop). In here, you should buy the Cushion, a gift for Roll, as well as anything else you haven't bought yet.
Check the dresser inside the General Store for 1,500 zenny.
Go inside the door marked 'Digout'. You'll find yourself inside the digger's guild. This is the main office for upgrading your license. The elevator leads to optional ruins (more on that later), and the door leads to the guildmaster's office. Since you have some experience under your belt now, how about talking to the woman and taking your Class S Digger's Test? If you don't want to/can't, skip ahead to the Guild Ruins, or continue with the game with the Nino Island siege.

Go:
Backward: Class A Digger's Test (OPTIONAL)
Backward: Returning the First Key
To the Walkthrough Home
Forward: Class S Digger's Test (OPTIONAL)
Forward: The Guild Ruins (OPTIONAL)
Forward: Siege on Nino Island, Part I