Usage patterns
〈人〉のコスプレをするto cosplay as (a character)
She cosplayed as her favorite anime character.
コスプレ姿で〈動詞〉to do something while dressed in cosplay
Everyone took photos in their cosplay costumes.
コスプレイベントに参加するto take part in a cosplay event
I'm planning to attend a cosplay event with friends next month.