Aaron L. Goosby/Kyuu

Secretly identified as naught but a Thought Projection named Kyuu, Erin Lamar Goosby is the six-year-old daughter of Aaron Lamar Goosby and a mage-in-training at Hydra Head.

Personality
Erin is a very meek girl. Much like her father, she is in possession of a rather extreme unwillingness to speak to the point where she's made a habit of substituting speech for gestures. Also, she generally does as she is told by just about anyone whom bothers to give her any amount of instructions.

Unlike her father though, she is brave enough to allow herself to be reliant on the assistance of others whenever she deems it necessary for her to do so. She's also willing to aggressively stand up for herself rather than simply ignore the problem like her father would.

It should also be noted that Erin is a very curious girl. So much so that a lot of her guildmates refer to her as The Nose as a direct reference to her nosiness.

Aaron Lamar Goosby
Erin as a love-hate relationship with her father. She admires a great many of the aspects of his personality, yet at the same time she loathes an equal amount of those aspects as well. To put it simply, she adores his generosity. But despises his pride.

Though she may work as his extra pair of eyes and ears within Hydra Head, she ultimately considers herself to be Aaron's enemy in terms of information warfare. Her goal is to expose all of Aaron's secrets. But she wishes to do so in a manner from which he can not escape.

She doesn't want to send Aaron packing. Instead she wants to force Aaron into confronting the consequences of his secretiveness and isolationism. So that he'll develop into a more open person and thus become a true member of Hydra Head.

Maturity Magic
Maturity Magic (Romaji: Ure no Mahou, Kanji: 熟れの魔法) allows Erin to manipulate the maturity of her body and or mind. Thus allowing her to shift between being prepubescent, adolescent, or an adult at will. Either physically or mentally. Though it should be noted that Erin can't manipulate her emotional maturity.