Sailor Moon R Part 2 is about the Black Moon. The reason I divided
this season is because, one, it is normally divided. And two, it
consists of two totally different plots. This season introduces Chibi
Usa (NA Rini). Chibi Usa is a mysterious girl who fell from
the sky one day while Usagi and Mamoru were enjoying a nice day off.
Unfortunately, to explain this in some detail there will be like two spoilers. First of all, Chibi Usa is the future daughter of Usagi and Mamoru. I don't know if that is considered a spoiler, but whatever. Anyway, the entire season is about new enemies from outer space. Specifically Nemesis, the 10th planet.
I didn't see this season to it's fullest either so the rest is sketchy. Anyway, a new enemy appears in Tokyo. Like all the other enemies so far, they specialize in stealing energy. Because it is spelled easier, I am going to use the NA names of the villains. Anyway, the first set of enemies are the four Sisters of Deception who are led by Rubeus.
So as usual the Senshi battle the enemies to save the world. This season has a ton of information. Their fighting eventually takes them to the future Crystal Tokyo where they encounter a few problems before returning to the earth for the final battle. During this season Sailor Pluto is also introduced though she plays a much smaller role than she does in the Manga. Well, that's the sketchiest summary I can think of. For a more detailed plot, click here.