A/N: So I was watching an episode of Shinsengumi and promptly wanted to do a whole thing with Harry finding a magical sword in his ancestral home or something that could deflect magic and whatever but apparently my fingers and my brain didn't agree bc this is all I managed. Feel free to take the idea (and the magic sword while you're a it) and turn it into something much more awesome and legible than this (and let me know bc I'll wanna read it~)
When Dudley was younger he'd gotten interested in Japanese cartoons that would sometimes show on TV and harry had taken to sneaking several peaks when he could while doing his chores. One of his favourite shows at the time had been one about so-called samurai, amazing sword wielding people who looked like they could take on the world and look graceful while doing it.
Due to both his size and situation, he'd always dearly wished he could wield a sword himself, as he felt it would be able to protect him against people like Dudley and his uncle. Of course, there was no way anyone in that house would actually allow him the opportunity to learn and fight with a sword.
It wasn't until he turned eleven and first set foot in Diagon Alley that opportunities started opening up for him. Between magic and his huge vault, he could surely afford a katana, lessons and a way to hide it all from everyone. These magic people didn't look like they liked muggles much and you could see everyone waving around the sticks they called wands. That certainly didn't look like a very sure way to defend yourself to Harry...
And so he invested in everything he could possibly need for his new training. He also looked around to see if there was any place he could hide out in and make his home, though it seemed unlikely the muggle world would allow an underage boy with a reputation like his live by himself...
As it turns out, asking the goblins was a great idea, as they pointed him to several surviving Potter properties he could move into. Harry chose Potter Manor, hoping it would help him find out more about his family as well; his real family.
Harry spent the remainder of the summer at his new home, looking for a tutor to learn how to wield a blade, and reading through his new schoolbooks. He'd never even thought magic was real; there was no way he wasn't reading ahead to see what he could expect!
Learning how to wield a blade would be hard, but he was more than willing to put in the required effort, and if it could save his life he would not hesitate to learn as much as possible. After all, this Voldemort guy was still out there according to Hagrid... Not to mention his followers probably wanted him dead as well, and Harry had every intention of surviving to experience living properly.