The title of the picture is "な、何ですかコレ！！ぬるぬるして甘いッ！！", which with my crappy Japanese skills and Rikai-chan translator is Ryou exclaiming something along the lines of "What is this?! It's slimy and sweet!!", and the author's comment is "葛だよ＾-＾ｱｯﾀﾏﾙﾖ", or "It's arrowroot (powder). ^_^ Of course." I think. That and the lack of a R-18 rating makes me think this isn't explicit, but it sure as hell looks that way. Feel free to change the rating, or correct me.