For a story, those close to me understand this well...

Amos: A human being, he has a mind he can't understand and he has never been himself, except for some sort and glorious times when he was blessed with the love of a person he could really trust and rely on for companionship, that person showed Amos who he truly is, that being: Kyo.

Kyo : A happy raver kandi-kid. He has been lost most of Amos's life, Kyo is a personality that belongs to Amos, the single and true self. He is happy, upbeat, fun, funny, responsible, loving, selfless, giving, healthy, and chill. He is like a child, but not childish, he is mature. Amos believed that Kyo was non-existent because of his lack of self and having only being able to live off examples of what he likes in other people. But the girl showed Amos that Kyo was hidden away his whole life.

Kyu : Scarred, scared, mentall/emotionally traumatised and hurt over the course of Amos's life. He is paranoid, easy to anger and depression. He is the mind of Amos's that is chaotic, untrusting, and thinks in paradoxes and oxymorons, causing great confusion for Amos. Kyu is not evil, but he certainly thinks this of himself for all the hurt he causes Amos and others. The scars on him are the mental scars of Amos. There is also the mask for many... good reasons. He bares all the burdens of Amos. He is somewhat a... self hating narcisist, and self-loathing, low self esteem ego maniac... yes, that's what is meant by oxymorons and paradoxes. Kyu has thought of himself as a demon, but the same girl who showed Amos that Kyo is the true him also showed Kyu that he is not evil... just mixed up and broken and hurt, he makes mistakes. She also showed him that the things he does are his desperate attempts to protect Kyo. Kyu has also healed a lot thanks to the love of that girl for him. Kyu is in control of Amos mostly, and has been almost all of Amos's life; but he believes that Kyo is the rightful controller, the right mind for Amos. He is in control to protect Kyo.

Two minds at once: Amos, when with the girl had for the first time had to deal with two minds, the transition to Kyo was long, but she made it easy. But when Amos had been severely hurt, it lead to complications with his mind, where there were switches between the two minds, and with each major trauma, it grows more and more difficult to heal, and takes more and more time to heal.