Aoko, though she is the protagonist’s love interest in her series, is not a main character and she doesn’t have a whole lot of given background information. As such, most things I have discerned about Aoko are purely head canon but can be supported with what’s been seen of her in the manga and how other characters act around her or when she’s not around.
First off, Aoko is not given a canon mother and since no one knows what happened to the lovely Mrs. Nakamori, I play it off like Aoko doesn’t know what happened either. Before I get into the likely long notes on Aoko’s psychology I should probably explain a bit about my head canon on the Nakamori’s and how it affects Aoko.
Ginzo Nakamori and his wife were never a rich family and when Mrs. Nakamori announced she was pregnant they found out she had a rare pregnancy complication that gave her a very small chance of survival, rather then go through with an abortion the woman wanted to give birth because she was just sure she was going to have a girl. As the pregnancy wore on it became apparent that Mrs. Nakamori’s body was not going to survive delivery as it had gotten too week. The strongest woman Ginzo had ever known was deteriorating and subconsciously he blamed it on his unborn child.
When the time finally came, his wife did indeed die and he couldn’t help but blame the little girl his wife had managed to bring into the world. He didn’t even bother to spend too long naming his brand new daughter and just decided on ‘Aoko’ or ‘blue child’ which is her birthstone. But his wife’s death only sparked more problems in the widowed man- being a police officer may have supported him, Aoko, and his wife but funeral costs and the hospital bill very nearly bankrupted the poor man so he couldn’t afford to take time off and adjust to the idea of having a baby. His superior, realized Nakamori was struggling and offered him a permanent position chasing Kaitou Kid as the head of the Kaitou Kid task force. -The reason Nakamori is so hell-bent on catching Kid is because he wants to thank his boss.
Because of this, Nakamori took Aoko to work with him everyday until she got to be a little bit older. Her earliest memory is a lady handing her candy while she’s sitting on her dad’s desk. Once she was old enough, Nakamori enrolled her in private piano lessons as he couldn’t afford daycare. Aoko didn’t even try to learn at first, she wanted to be with her dad at the police station but he convinced her to be a good girl and make him proud.
Once she was old enough to go to school he told her to wait for him by the clock tower until he got off work. Which she did, fearing that if she moved from her spot her dad would go home without her. She knew Kaito from school but he was probably a little terror and she didn’t talk to him until he met her on the steps of the clock tower.
After making friends with Kaito she no longer had to wait alone at the clock tower but she probably insisted they didn’t move too far away from it until Nakamori finally bothered to come up with some find of deal with the Kuroba family and arrange it so he could just pick Aoko up from their house everyday. Which, of course the two children had no problem with and I imagine Toiichi more then willingly agreed too. From then on Kaito and Aoko were never a part for more then a few hours and Aoko likely fell asleep over that the Kuroba residence on more then one occasion.
In the second chapter of the manga Kaito talks to the inspector and they talk in a way that made me realize Kaito and Ginzo are not close but, Aoko seems to be close with Kaito’s mother. So I don’t think Ginzo is around the kids that often. Aoko is a constant reminder of what happened to his wife and because of this, he has distanced himself from her. Though, of course, he still maintains his fatherly instincts if she’s in trouble or something. And, of course, if she asks him for anything, he bends and says yes, provided his job allow it.
Aoko is not close with her father, she wants nothing in the world more then to have a close and healthy relationship with her dad but he’s never around and he has purposely distanced himself from her. So she took everything he said seriously. Especially when he caught her in a lie and told her that lying always proceeds stealing and he’d have to arrest her if she ever stole anything. Aoko, of course, never told a lie again and likely got onto Kaito if he tried to lie about something... and probably tattled on him. A lot.
The chapter ‘Hustler vs. the magician’ bothers me in the sense that Nakamori does not recognize his own daughter-even if her hair was done up and she was dressed up- he still should have been able to recognize who she was. Especially after she slips and calls herself ‘Aoko’ and definitely when she mentions Kaito’s name. Neither of those things made the inspector even a little suspicious. Ergo he does not pay much attention to his daughter.
Toiichi’s death hit both Kaito and Aoko hard, Kaito harder for obvious reasons. But Aoko had felt her whole world had shattered because suddenly Kaito wasn’t his usual cheery self. It was probably around then Aoko started learning from Kaito’s mom how to cook otherwise, the magician would probably just get in the way and annoy Aoko.
With Toiichi’s death came the mysterious disappearance of Kaitou Kid and Nakamori worked overtime. He probably didn’t want to accept the rumor that Kid had died and abandoned all his duties as a parent to find the thief. Which took 8 years. But Aoko didn’t mind much, her dad’s job was important and far more important then she is so she was content to continue hanging about the Kuroba house as Kaito slowly recovered from losing his dad-though he likely never did fully recover, just learned how to throw a mask up.
Shortly after Aoko turned sixteen Kaitou Kid returned but this time Kaito wrapped up in the kid case too, being a fanboy and all. Aoko didn’t voice her discomfort. Kaitou Kid was obviously more important then her and shortly after the thief’s return Kaito picked up a night job with an old friend of his dad’s. Aoko would have felt selfish if she were to tell him she felt left out and little lonely, so she didn’t and from that point on decided she would just ignore the things in life that were potentially upsetting to her. Besides, she still had her other best friend Keiko- at least, until Keiko decided that she would become a fan of the thief too, leaving Aoko to feel like an outcast because she hated the thief.
Aoko does not see herself as important. This is because she has had to take a back seat to Kaitou Kid all her life. And if her mother left she had to left Aoko at a young age-far too young to leave her with a father that was a workaholic at the extent that Ginzo is. And because Aoko is under the impression her mother left and her dad is more concerned about Kid then his own daughter she’s come to the conclusion that no one really wants her around and she’s only in the way. Kaito, Hakuba, and Akako all unwittingly help prove her right.
Aoko is happy to have company when she gets it and does not usually turn people down unless they’re downright creepy to her. And as we can all see from ‘sunken pirate ship’ that’s not a lot of people. She loves helping because it gives her a feeling of being useful.
She’s not stupid. None of the leading Gosho girls are. She knows what Kaito’s doing but she’s turned a blind eye to it and has been in denial about it ever since figuring it out. She won’t confirm it with him though, she could be wrong and she clings to that hope. Because if Kaito is Kid then she has to choose to either tell her dad and betray her best friend or keep quiet and betray her dad. It’s his life’s ambition to catch Kid, what would he say if he found out his only daughter knew who Kid was this whole time?