One Piece is the most popular manga in the world, recently overselling the Spider-Man comics and close to overtaking Batman's worldwide sales. It's also sold double what Naruto & Dragon Ball has overall. So it wouldn't be surprising to say that many new and upcoming mangakas use One Piece as inspiration for their own manga, especially so since One Piece dominates in Japan - in terms of TV ratings, merchandise etc... In simpler terms, it's EVERYWHERE in Japan. (One Piece Cafe) That brings me onto my belief that Hajime Isayama, author of Shingeki No Kyojin, took some inspirations from the pirate manga for his own post-apocalyptic manga. When I first read the Uprising Arc back in 2013, I couldn't help but notice similarities between the government/establishment of the Walls & the World Government in One Piece. As the arc progressed and the story continued, I found more and more similarities (SPOILERS). Both series deal with a corrupt government hellbent on censoring what they don't want the public to find out, going as far as killing people & erasing history to do so Attack On Titan - King Fritz erased the memories of humanity so that they would forget that humanity existed beyond the Walls, the government banned technological advances like hot air balloons so people couldn't see what was outside the Walls, Erwin's father was killed by the Military Police for his belief that the Wall government was covering up the true history & that there was a possibility that human life existed outside the walls. One Piece - The World Government eradicated any evidence linking to what happened in the Void Century & to the existence of the Ancient Kingdom, they banned the study of the poneglyphs (as they were indestructible and unable to be destroyed), the island of Ohara was annihilated from the map by a Buster Call because the archaeologists there were studying the poneglyphs & successful in uncovering the existence of the Ancient Kingdom and the fact it was destroyed by those who would later become the World Government. http://onepiecepodcas****m/wp-content/uploads/2016/04/Screen-Shot-2016-04-06-at-4.23.19-PM-1.jpg Both series contain true royalty who abdicated their thrones and let stewards take over Attack On Titan - The Fritz family changed their name to Reiss and hid in the shadows while a fake royal family took over as the ruler of the Walls. One Piece - 19 out of the 20 Kings left their thrones and ascended to Mariejois to become Celestial Dragons, while stewards took their place in ruling their islands (e.g. the Riku Family replaced the Donquixote Family in Dressrosa) Both series keep readers coming back because of massive mysteries relating to their own worlds & histories Attack On Titan - The basement, the history of the world (including when the titans showed up), what's outside the walls etc... One Piece - Raftel, what happened before and during the Void Century 800+ years ago, the Will of D, how is it all linked etc... Both series involve a great kingdom that once ruled the world but was then destroyed by an external enemy, who went on to become the new 'rulers' of the world Attack On Titan - Eldia once used its titan might to subjugate & rule the world, but during the Great Titan War, the Marleyans won and became the new powerhouses of the world -- the remaining Eldians were allowed to live but became secondary citizens One Piece - The Ancient Kingdom once presumably ruled the world and believed in the unity & freedom of all races (look at the Mink-Kozuki alliance, look at the promise between Joy Boy & the Mermaid Princess), but during the Void Century, something occurred which led to their destruction by the 20 Kings, who then formed the World Government -- the descendants of the Ancient Kingdom, presumably the D. Clan, lived on but forgot their past. Both series have a protagonist whose father is/was the leader of a revolutionary army Attack On Titan - Eren's father Grisha became so hateful of the Marleyans that he accepted an invite to the Eldia Restorationists. Later on he became the leader of this group and dedicated the rest of his life to overthrowing Marley and restoring Eldia One Piece - Luffy's father Dragon is the leader of the Revolutionary Army (though details of why he formed it (if he did) are not currently known). He dedicates his life to liberating various countries around the world, with the end goal of overthrowing the World Government. With that being said, it's no wonder that Attack On Titan successfully managed to overtake One Piece in half-year sales once back in 2014, the concepts are very similar (and yet the execution is extremely different), keeping readers coming back for more. These two are the only Shonen which execute the government conspiracy storyline so brilliantly. And let's not forget about this (lol): Hope you had a great read!