It does wrap up nicely, it short of hinted at a second season but not strongly enough to spoil the warm ending.
There are some girls but they are minor characters at best, the girl by the fence gets the most involved with the main plot, but as the episodes go on they take up less and less space (not that they ever take up that much anyways)
The story is about the red headed boy (Yuki) who moves to a new town where he meets an Alien boy who becomes his friend and together they save the world. It has a very comfortable tone and is really things like about social anxiety, finding yourself, the importance of friends and family.
I love it to death, I watch it every summer as it has a super summery feel to it and definitely recommend it