Well, a possible plot is that Harry Potter, as a mafia boss, has a very different set of moral and ethical rules compared to what he was taught at Hogwarts. Daphne enters his world because she is on the run from some dark wizards who are after her family's fortune. Harry offers her protection in exchange for her help in some of his more delicate operations. As they work together, they find that they are attracted to each other's strength and intelligence. And their relationship blossoms against the backdrop of the dangerous mafia - like wizarding underworld.
A really interesting plot could be that the wizarding world has a hidden mafia - like structure that has been operating for centuries. Harry Potter, after leaving Hogwarts, stumbles upon it and rises to become a boss. Daphne is a part of an old pure - blood family that has some knowledge of this underworld. She initially tries to stay away from Harry and his newfound power, but circumstances force her to interact with him. As they interact, they start to understand each other better. Harry realizes that Daphne is not just a typical pure - blood snob and Daphne sees that Harry is more than just a powerful mafia figure. Their relationship then becomes a central part of the story as they navigate the dangerous world of the wizarding mafia together.
One plot idea could be that Harry, as the mafia boss, is trying to keep his identity a secret from the wizarding world while Daphne accidentally discovers it. She then has to decide whether to expose him or join his cause. Another could be that they team up to take down a common enemy in the criminal underworld of the wizarding community. Maybe there's a dark wizard who is threatening both Harry's mafia operations and Daphne's family business, so they form an alliance and in the process, develop romantic feelings for each other.
One plot idea could be that the mafia boss is secretly protecting Hogwarts from a new dark threat. He uses his underworld connections to gather information that the Ministry of Magic can't access. For example, he might discover a group planning to steal powerful magical artifacts from the school. Another idea is that the mafia boss is actually a wizard who was exiled from the wizarding world long ago and has built his own criminal empire in the Muggle world. But when he hears about Voldemort's return, he decides to use his resources to help Harry Potter, in his own unorthodox way. A third idea could be that the mafia boss has a vendetta against a Death Eater who once wronged him in the past, and he teams up with Harry and his friends to take the Death Eater down.
The mafia king could be a new threat that emerges after Voldemort's defeat. He sees the power vacuum in the wizarding world and decides to take over. Harry, being the hero, has to gather his old friends and some new allies to face this new menace. The fanfiction could explore how the wizarding world has changed after the big war and how it copes with this new type of threat.
At first, Harry and Daphne's relationship could be based on mutual suspicion. Harry may think Daphne is trying to infiltrate his mafia operations for some other powerful wizarding family, and Daphne may be wary of Harry's new and dangerous lifestyle. However, as time goes on, they are forced to work together on a task. During this time, Harry shows Daphne the parts of the wizarding underworld that are in need of change and protection, and Daphne shares her knowledge of the wizarding society's upper echelons with Harry. This sharing of knowledge and experiences draws them closer. They start to rely on each other more and more, and slowly, romantic feelings begin to develop between them.
One plot idea could be that Daphne Greengrass discovers she's pregnant during a time of great unrest in the wizarding world. Maybe she has to hide her pregnancy from certain dark forces who would use it against her or her family. She could seek refuge with some of the more neutral or light - sided characters from the Harry Potter series.
One idea could be that Harry and Daphne are paired up for a special project at Hogwarts. As they work together, they start to see each other in a new light. Daphne might initially be a bit cold towards Harry, but as she gets to know him better, she warms up. Their relationship could develop slowly as they face challenges within the school, like dealing with a new dark magic threat.
A possible plot for 'Harry Potter mob boss fanfiction' could be that a former Death Eater who survived the war decides to create his own criminal empire. He recruits other disgruntled wizards and witches who feel they were wronged after the war. Harry, now an Auror, has to go undercover to gather evidence against this new mob boss. He has to face many challenges as he tries to blend in with the criminals while still holding onto his own moral values. This could lead to a lot of internal conflict for Harry as he sees the reasons behind some of the wizards' actions while still knowing that what they are doing is wrong.
A really interesting plot could be that Harry and Daphne find a hidden chamber in Hogwarts that is related to an ancient magic that neither the Gryffindors nor the Slytherins knew about. They have to work together to keep it safe from dark wizards who are also searching for it.
One idea could be that they initially resist the betrothal. Harry is suspicious of Daphne because of her Slytherin heritage, and Daphne thinks Harry is just a fame - seeking Gryffindor. But as they are forced to spend time together for various magical tasks assigned by their families, they start to see each other's true natures and gradually fall in love.
Maybe there could be a plot where they face opposition from some quarters. Some might not approve of a union between Harry and Daphne due to their houses' historical rivalries. They would then have to overcome these prejudices and prove that their love is stronger than the old grudges. This could involve them going on a quest together to show that they are a united front and are meant to be together.
One idea could be that they meet in a magical library. Harry is researching a rare spell and Daphne is there looking for knowledge on potions. Their eyes meet, and from that moment, a connection begins. They start secretly meeting to exchange their findings, and slowly, their relationship blossoms into love, leading to marriage.