His cheeky grin and the way his head is tipped towards the girl show he his definitely interested. She is staring back in a submissive way and has tucked her hair behind her ear on the side closest to him, all female signals of interest. The girl has also managed to almost drape herself over his leg, giving him a better view of herself and making him think of her in a more intimate way.  By placing his leg into her space, this guy is indicating that he is very attracted.