One Piece/Negima crossover: Where the Straw Hat crew crashes into Mahora and help out Negi with his adventures thus leading to Negi and his class joining up with Luffy on his quest to become the Pirate King when they return to the One Piece world during the usage of the Cassiopeia as they travel through time or when Negi's group, the Ala Alba, gets transported to the Mundus Magicus with a few extra tagalongs they are instead transported to the One Piece world by mistake.

Also, you could have this happen: when the Ala Alba transport to the Mundus Magicus they are accidentally scattered to different islands in the canon One Piece world while at the same time joining Luffy's crew in order to get back together again.

Note: If first choice, then all current crewmembers up to the beginning of the Skypeia saga must already have joined and if second choice, the story must go through East Blue saga through New World Saga and onwards in manga. Also, Luffy must have a harem as well with all the girls that he made an impact on by beating the asses of certain scumbags or giving them a much more positive outlook on life like Nami, Vivi, Robin, Conis, Camie, Marguerite, Boa Hancock, and Shirahoshi. Feel free to add any other girls that you think might work for the harem, but only if they are not connected romantically with any of the other male Straw Hats. Also, Negi must have all of 3A in his harem, too.

Please bare with me if any of this seems outlandish, but I am mentally starved for a good One Piece/Negima story and I have no talent as a writer. I would be happy to proofread it for you if you would let me. Thanks for taking the time to read this and good luck with your all your stories!