Uhh, Wakana tagged this as Hatsune Miku. I don't really know what this design is, if it's an original outfit or cosplay or whatever (I also don't know what the "World is Melting" thing is).

Here's what Wakana has to say about it:
和訳：　世界が君にめろめろなのさ　　　　　夜明けのテンションで描きあげてしまっていろいろ後悔しています。

世界が君にめろめろなのさ
-> The world is mad about you. or The world fall in love with you.

I think the phrase "World is Melting" is just Wakana's mistake - He/She must have used Japanese to English translator.

(addition)
めろめろ means melting or flaring, and also refers to fervent, enthusiastic, or fascinated, metaphorically.

Wha? I thought meromero meant 'mellow', used kind of when you're in love with someone.

AFAIK, it can mean flaring, but the love-related usage comes from its other meaning of "soft, loose" (=> soften up).

Melt is a Miku original song. I'm inclined to believe this is her.