Just for the curious, this is actually the opening to the Di Gi Charat Fantasy game that was made for the Sega Dreamcast waaaaay back in the day; there's currently a PS2 version now, as well. :3
Basically.. Dejiko shoots a huge Mekarabeam that opens a weird portal and sends everyone inside it, icluding herself.. due to the impact, she loses her memory and it's up to you to help her and get back home.... that's everything I know because the game is very obscure xD I think it has multiple endings too