They might run away to Muggle London. There, they experience the simplicity and complexity of Muggle life at the same time. Draco could be fascinated by the technology, while Harry tries to adapt to a life without magic for a while. They could also meet some Muggles who are surprisingly aware of the wizarding world in a very different way, which adds an interesting twist to the story.
One idea could be that they run away to a hidden magical land where they discover a new form of magic that is neither light nor dark. They have to learn to control it together and in the process, they become closer friends. Another plot could be that they run away because of a false accusation against them in the wizarding world, and on their journey, they find evidence to clear their names.
Maybe they are running in a magical race. Harry uses his broom - flying skills in parts where he can, but Dudley, being more used to running on the ground, finds shortcuts through Muggle - like alleys that are magically connected. Along the way, they meet various magical creatures that either help or hinder them, and they have to figure out how to deal with them as a team.
One idea could be that Harry and Draco find a magical toy that has the power to transport them to different wizarding worlds. They have to work together to find their way back home. Another could be that they both inherit a collection of enchanted toys from an old wizard, and they must figure out how to use the toys to solve a mystery in Hogwarts.
One idea could be that Harry and Draco find an abandoned magical baby and they have to work together to take care of it. This forces them to put aside their differences and learn about each other in a new way.
One idea could be a story where Harry, Draco, and Severus are forced to work together on a dangerous mission to save Hogwarts from a new dark threat. They start off distrusting each other but gradually learn to respect and rely on one another.
One idea could be a story where Draco, Harry and Hermione are forced to work together on a special magical project for the Ministry. They start off hating each other but gradually come to respect one another's skills. Another plot could involve them getting trapped in an alternate magical dimension where they have to rely on each other to find their way back. Maybe Draco has some knowledge of the dark magic that created the dimension, Harry has his Gryffindor courage to lead them through dangerous areas, and Hermione uses her vast knowledge to figure out how to break the spell that trapped them.
One plot idea could be that they are forced to work together on a school project that requires them to explore each other's family histories. This makes them realize they have more in common than they thought. Another could be that they discover a secret magical realm only they can access together, and in the process, they form a bond. Or perhaps they are both framed for a crime and have to rely on each other to clear their names.
Well, in this type of fanfiction, a possible plot is that Harry is sold due to a powerful curse placed on his family. Draco, who has a change of heart over time, tries to break the curse. This could lead to a journey of self - discovery for both of them. They might also discover secrets about their families' pasts that are intertwined. Also, the situation could force them to work together against a common enemy that emerges because of Harry's new 'ownership' status.
A possible plot is that there is a mysterious dark wizard on the loose who seems to be targeting both Harry and Draco's families. They must put aside their differences and work as Auror partners to protect their loved ones. Along the way, they discover secrets about each other that they never knew before, like Draco's hidden acts of kindness during the war that Harry was unaware of. This new understanding helps them bond and fight the common enemy more effectively.
One idea could be them having to deal with the reactions of their friends and family. For example, Harry's friends from Gryffindor might be initially shocked but then come to accept it as they see how happy Draco and Harry are together. Another plot could involve them facing some sort of magical mystery or threat that only their combined skills can solve, which also strengthens their bond as a married couple.
One plot idea could be that Draco accidentally drinks a love potion meant for someone else and he starts acting strangely towards Harry. Harry is initially confused but then realizes what's going on and has to find a way to reverse the potion's effects while also dealing with his own mixed feelings for Draco.