One of the four core protagonists of Eternal Storm and plays a prominent role from Eternal Rain: REVISTED into following arcs.

Bio:
Atsuko comes from an average family, living with her older sister and her parents.
She's quick to argue and poke fun, but knows when to get down to business -- and she's got to be where the action is. Atsuko is infamous for the nicknames she gives people.

Relationships with other OCs:
Toki - Her evil big sister. (Okay, not totally evil, just bossy and annoying.)
Shiori - A crybaby who can be a pain in the butt.
Takeshi - He treats her like a kid, which annoys her because he's not that much older.
Reka - He also treats her like a kid, but if he gets too annoying, she knows how to push his buttons.
Toshirou - He's a bit of a klutz and a dummy, but it's hard not to like him when he tries so hard.
Sora - He's too nice to pick on.
Nasim - She's bossy and stuck-up.
Takumi - He's too hung-up on the rules, and they don't get along.
Taki (Kobayashi) - She considers her a buddy, though she's a bit too goody-two-shoes.
Hideo - [SPOILER]