Emotionless Hitokiri
She knows she's a girl... I mean, she still has her memories and all from the real world. She just doesn't want to tell anyone else. I guess you could say I'm paranoid, but I wouldn't try to reveal that much about myself.
Wrong. Tsukasa's the Angst Master, so she decided to make her character a boy in order to further escape her real life. When she was Data Drained, Morganna erased all her memories except those about her angsty, emo life, and created memories to make her believe that she was male, and Morganna was her mother.
Until she started resisting Morganna, Tsukasa fully believed she was male. After being asked the question several times and questioning it herself, though, she started to realize that she was really female. Bear knew it all along, and Mimiru was a tad skeptic, but Tsukasa was the one who confirmed it near the end of the series.