Ill try to clear it up a bit more, though its difficult without spoilers due to the mystery nature of DS 2's story. So basically, there is a service going around known as Nicea. Nicea lets people see videos of their friends dying that later seem to come true. Shortly after the main character signs up, all of Japan is under attack by demons. Nicea ends up giving the characters the ability to summon demons of their own and the story revolves around the characters trying to 1. survive and 2. protect Japan and the world. Neptunia on the other hand is about the goddess Neptune, 1 of 4 goddesses who embody consoles. She lost her memories after a battle with the other goddesses, discovers monsters on the loose and then ends up going to hunt them. Theres more to it than that but it proved to be boring writing to me (the characters felt like extreme stereotype characters to me and the writing didnt seem to help at all) so I stopped watching early in and can't provide more insight. Again, note that my descriptions/endorsement is biased but hopefully this helps a bit
