This is fanart for the fanfic Harry Potter and the Methods of Rationality, Chapter 21.
"I have been on a date, scion of Malfoy. My first date. And when I call that favor due, you will pay it."
edit: I fixed Harry's hair so it's clearly black and thus not Malfoy's.
note: They are near the mini waterfall mentioned in the chapter, which Harry thinks looks like snot