A 'lock and key novel' is a type of novel that often involves elements of mystery or secrecy. It might be centered around a locked room mystery, where the key to solving the mystery is like a key in a lock, unlocking the secrets within the story. For example, in some detective novels, the detective has to find the key piece of evidence (the 'key') to unlock the truth about a crime (the 'lock').
I'm not sure specifically as I haven't read it in detail. But generally, a 'lock and key' concept in a graphic novel might involve themes of mystery, like finding the right key to unlock a secret or solve a problem.
Since there's not much information given, it's difficult to give a detailed account. However, generally speaking, if 'aja romano hamilton is fanfic' is indeed a fanfic, it could be a work of fiction written by someone named aja romano. It might explore different aspects of a Hamilton - based story. It could be about an alternate universe for Hamilton, or it could focus on relationships that Hamilton has in this fan - created story. Without reading the actual fanfic, all we can do is speculate.
One common theme could be friendship. Since Aja and Steve are characters in the same story, their friendship might be explored in different ways in fanfiction. Maybe how they support each other through various challenges.
There could be a situation where a little girl, while playing a prank on her brother, secretly stuck his key inside the lock of his bicycle. She thought it would be funny to see his reaction. But her brother got really angry when he couldn't unlock his bike to go to his friend's house. In the end, she apologized and they found a way to get the key out together.
I don't know the main characters in 'lock and key graphic novel' as I haven't read it. You could try looking for reviews or summaries online to find out.
In 'under lock and key fanfiction', it may deal with power dynamics. For example, one character might have another character under their control, much like something being locked away and only accessible or manipulable by the one with the key. It could also be about a hidden society or group that is 'under lock and key', meaning it's very exclusive and secretive, and the fanfiction explores the inner workings of this group.
One example is 'The Murders in the Rue Morgue' by Edgar Allan Poe. It has elements of a locked room mystery which is a characteristic of a 'lock and key novel'. Another is 'And Then There Were None' by Agatha Christie, where the mystery on the island is like a locked enigma and the detective has to find the keys to solving the murders.