Or a School/Gang AU, where Ace is just moving to a new school after his last school miraculously got set on fire. Ace is the head of the gangs in the grey terminal, he is a fair and just ruler that keeps the gangs in line, he is also one of the masters of the jungle, someone who knows the jungle like the back of his hand, Ace is also someone who is lucky enough to be able to go to school. Ace wants to become an engineer, he wants to build things like no one else and wants to help the people of the Grey Terminal. So Ace tries his best at school, but when his gang life and school start to mix, Ace's grandfather decides Ace and Luffy and Sabo need to move schools, to Raftel High in the Grand Line, a place that Ace hates cause his father was the founder. Garp knows this and he also knows how much trouble it would be if people found out who Ace is, so Garp enrolls Ace with his mother's name and Ace fits right in, he befriends Trafalgar Law and Kidd who isn't as bad as his reputation says, sure he can beat the snot out of anyone, but only anyone that pisses him off to much and anyone that hurts his friends. And then Marco and the White Beard pirates gang comes in and they try to befriend Ace who gives them the cold shoulder, knowing better than to get involved with the white beard gang, especially since he's the king of the grey terminal, but the White beards persist and with time Ace grows to like all of them especially Marco, who he's growing a crush on. But soon the problem of the gangs of the grey terminal comes to Ace in the Grand Line, and Ace takes care it, but problems continue building and persisting and it isn't long before the White beard pirates notice the amount of gang fight going up in the area, they don't know that Ace is the king of the Grey terminal and is the reason the fights are going up.
In school, Ace and Marco have to do a play together and during the process they realize they have feelings for each other and they start dating. Ace is trying to tell Marco that he is the king of the grey terminal and Marco is trying to tell Ace that he is in a gang. Though before anyone can tell each other anything, the White beard pirates realize that the grey terminal is the reason that the gang fight in the Grand Line have escalated and they go to the Grey terminal to see what's wrong they meet Ace there and they realize that Ace is the reason and take it pretty well but Marco is a little hurt that Ace didn't tell him, but when Ace explains that he was trying to tell him they make up. The White beard pirates then help Ace take care of the grey terminals problems and Ace and Marco soon get married.