This manga plays into the creepiness of tongues. It relies on gross-out techniques to make readers feel uneasy--showing a bulbous tongue, so big it leaves no gap between it and the upper lip, slobbering and covered with sores and ridges. The tongue looks like a turd. Licking is a very intimate act, so it creates a sense of discomfort seeing a stranger licking someone and sticking feir tongue in feir mouth. There is also the unease which comes from seeing unexplained phenomena.
I didn't really care for the ending, because it felt strange that the tongue seemed interested in Miku's love life.