This is based off a MUGEN character, apparently named Kujo Meiling (空条美鈴), who is a mix between Kujo Shoutarou and Hong Meiling. Artists comments - the bare midriff is because he likes it, the 2p color suits her better, and Star Platinum (her stand thingie from the game) doesn't look good with her so it's not included.

Is this cosplay taggable?

Since it's a kind of fusion, it's not cosplay and if, like you say, it's a MUGEN character(that could be drawn by other artists and uploaded here), kujo_meiling tag should be added.

Character tag changed to reflect Danbooru romanization standards.