They're all costumes from the game. I love that game...
Anyways, Here's how to register on pixiv:
1. Click the orange "Sign Up" button to the right on the main page.
2. Enter info
3. Done. Search away.
O_OIt's easy enough. You can tell what everything is without knowing it.
~You're on the phone to your girlfriend, she's upset
she's going off about something that you said
but she'll never get your humor like I do...~
IN OTHER WORDS, HAI.