Instructions
Play through the game until you have captured the criminal, who you find out is actually Beauregard, and duel him. When you complete this duel, a new duelist icon appears on your map.
Follow the icon on your map to find Mototani, then duel him. When you finish beating him, you will get a message from one of the Obelisk Blue Dorm students telling you that Crowler wants to meet you by the lake. A map marker will be added.
Go to the lake to meet Crowler to discover that it was all a ruse set up by Chazz, who wants to avenge his friends, who you defeated earlier. Beat Chazz to unlock two more duelists, Mindy and Jasmine, both of whom will be added to your map.
Level up to level five. If you're fairly close, as in level four with just a few more points to go, head over to Mindy and Jasmine and fight them to reach level five. Otherwise, find some other duelists and keep battling them until you are at level five.
Defeat Mindy and Jasmine. Shortly after the duel, you will get an email from Alexis asking you to head over to the Obelisk Blue Girls' Dorm.