Shumi's Lost Coin

Level Requirement: 20

Description

Talk to Shumi in Kerning City. She is just outside the Subway Station.
Go inside the Subway. Ask the Subway Worker for a Ticket to Construction Site B1 (cost: 500 mesos)
Complete the jump quest and double-click on the chest. You will acquire the lost coin.
Return to Shumi.

You can get one of these sets of scrolls:

In addition, you will also get

The first section of the jump quest

You start in Line 3 Construction Site B1 Area 1
When you enter you get to either take the top route (shown in red arrow above, not fully shown though) or the bottom route (in green arrows). Generally I find the bottom route easier. You will need to make through the electric bars and the "flying electricity".
The two routes come together at the chamber that is to the right of the chamber you start in. After completing that, you get to go to Line 3 Construction Site B1 Area 2.

The Stirge Area

In this area you have to jump up many platforms that make up an "S" shape, then climb up a ladder. All the while fake Stirges will cause you to fall.

Subway Depot. Click for full-size picture.

When you complete that stage you get to the Subway Depot! You can get out of there via double-clicking on the Treasure Chest, or you can train on the bubblings in the train. Be aware that after your 99-minute time limit you will be automatically ejected out of the area.

The Stirges and Jr. Neckis inside are invincible. When hit the result is always a "miss" and they deal 1 damage to you each time you knock into them.
This quest can be repeated. Doing so will give you 2 random mineral ores (of the same type). It seems, though, that Gold Ore is never given from this quest.
In each chamber there is an Exit sign NPC. Double-clicking on it will get you out, but that will effectively make you lose the 500 mesos you paid for the ticket.