A crossover journey beginning in Armed Girl's Machiavellism. He wields the world's strongest invisible magic sword, Yun Yao.
Nomura Fudo: "You're just like Inaba Tsukuyo, senpai. I can't see how you draw your sword at all."
Natsuki Subaru: "He transmigrated a little earlier than I did. It's great that we work in the same mansion. Before I even saw him draw his sword, he passed by the Bowel Hunter and slashed three times in the blink of an eye. Now that's a real transmigrator! I demand a power-up to my setting."
Reborn: "Is this man from the Sword Demon clan? I can tell that his casual movements reveal swordsmanship far beyond what someone his age should be capable of. His hands don't even have the calluses left by years of hard training. Could he have grown stronger before becoming a child the same age as Tsuna? And he's not one of the Arcobaleno."
PS: Most of the above is planned content. The protagonist is an original resident of the Armed Girl's Machiavellism world. The first few chapters will explain in detail the manga's original story and the settings from its earlier work that weren't mentioned in the anime, so readers who have only watched the anime, as well as those who haven't watched it, should be able to follow along (probably...).
