Too all you people wondering about why this is ending and why they don't just continue after they start dating:
Read the title of this manga.
The entire flipping premise, selling point and core of all the jokes and stories is about the two main characters being dense and not knowing anything about love or recognizing it. Once they finally realize what's going on and that they're actually in love, then it makes sense that the manga ends too, since it takes away the entire being that is the manga.
Now, that being said, there's nothing preventing the author from making a sequel ("We are first timers in love"), a spin-off ("I want rom-com love" or "Booby-chan's love after love") or a second season of this with new characters in a similar situation.