The sailor uniform is an item of clothing in some video games. It can only be worn by female characters. The male alternative is the stuffed collar uniform.
Stardust Accelerator
In Yu-Gi-Oh! 5D's World Championship 2009: Stardust Accelerator, it can be unlocked by unlocking all Tag opponents in World Championship Mode.
Reverse of Arcadia
In Yu-Gi-Oh! 5D's World Championship 2010: Reverse of Arcadia, it can be found in the puzzle room of Zeman's castle.
Over the Nexus
In Yu-Gi-Oh! 5D's World Championship 2011: Over the Nexus, it can be found in the Duel Monsters Spirit World.
Female Player (WC11) in Sailor uniform.