Sakuya is Rena, Flan is Satoko, and Remi is Rika. Their faces are even alike. I'd almost go so far as to say it might be a very elaborate photoshop of Higurashi art.
This isn't cosplay. It might have been a trace, but those are Sakuya, Flandre, and Remilia dressed as Sakuya, Flandre, and Remilia respectively. I'm removing the cosplay tag and the tags of the characters that aren't in it. Not sure it should have anything more than the parody tag, but I'll leave it to a more experienced user to determine if the Higurashi tag should stay.