Basement Ticket

Basement tickets are required to enter the Subway and complete Shumi's quests in Kerning City.

To get a ticket: You need to unlock the quests (by reaching Levels 20, 30, 40 and talking to Shumi). Once unlocked, talk to the Ticketing Manager inside the subway. He'll offer to sell you the ticket to the quest area.

If you've unlocked the second quest, you can still buy the first ticket. Same goes with unlocking third quest and buying first and second ticket.

Note that the tickets are for specific quest areas. A character can enter the general subway area at any time (though level 20 is recommended).