Custom Character Creation:
This feature becomes available when you complete the first Island. When you have beaten Fafnir you will be able to create a customised character in the Cafe/Multiplayer room by talking to the girl behind the counter that is to the left of the door.
Complete the following tasks to unlock the corresponding character.
Complete Story mode, then talk to Strea as Kirito. Complete the battle against Strea.
Complete Story mode, then talk to Sumeragi on a floating island in Woglinde, standing next to a chest after dueling Rain as Kirito.
Complete the game, then talk to an Undine at the plaza. Enter the dungeon in the top right of the map on Nibelheim.
Complete the game, then complete the short storyline quest with Seven by entering Agil's shop after completing the sub-events with Rain.