If you liked the History's Strongest Disciple Kenichi manga, the Anime-Planet community thinks you'd like:
When Gangryong was in middle school, a powerful martial artist named Yoochun saved him from a group of bullies. Eager to become stronger, the boy begged Yoochun to train him; and after several years of preparation, the man finally agrees to teach him his special skill, Lightning Fist. But soon, Gangryong is approached by a seedy organization named Reunion with a message: Yoochun is dead by their hands, and as his successor, the boy must become a member of Reunion. Once he becomes as strong as his deceased mentor, Gangryong can know more about Yoochun's death. And so, the would-be martial artist heads to a special school for Reunion candidates, eager to fight foes and allies to prove his strength along the way.
Both anime are focused on martial arts and the main character is suddenly taken to somewhere to to learn martial arts and eventually after a few months they become so strong that they can take down people who've been training all their lives and eventually fight against another group other than theirs.
At first glance, Kimihiro Watanuki appears to be a normal high school student; but little do people know that not only is Watanuki able to see spirits, but he's also a magnet for them! One day, after being chased by one such spirit, Watanuki happens upon a strange building. There he meets a mysterious witch named Yuuko, who claims she can get rid of his ability to see spirits - for a price: Watanuki must work as her housekeeper until he has paid off the cost of granting his wish. Now Watanuki's eyes are being opened to an entirely new side of the world as he assists Yuuko in her work, all while balancing the housework, his schoolwork, and most importantly, ensuring that Yuuko is never out of sake!
Both Zippy Ziggy and History's Strongest Disciple Kenichi feature a physically weak boy who joins (or is made to join) a dojo in order to become strong. Both of those series also feature a very strong female lead who pretends to be weak and who is already part of the dojo. You could say that the main duo in History's Strongest Disciple Kenichi are nice kids. Compare to them their Zippy Ziggy counter parts are massively messed up. Although Zippy Ziggy doesn't contain as many fights as History's Strongest Disciple Kenichi, you're probably still going to enjoy one if you liked the other.