Unsolved mysteries are all too common in the anime world. Certain plot points, backstories, or character motivations are left hidden, purposefully or otherwise. Sometimes, this is done to create suspense and encourage discussion among fans until the release of a new episode or season. Occasionally, however, creators forget to answer the very questions they put in place, or a series is canceled before viewers get to know the real truth. The following are the top ten unsolved mysteries that have kept anime fans scratching their heads for years.

10 Where Does Saitama's Strength Come From?

One-Punch Man parodies shounen archetypes, which means that Saitama is absurdly strong -- he can defeat any enemy with a titular one-punch. Many viewers have speculated over the years as to where Saitama got such incredible strength. It's unlikely that a true answer will ever be revealed, however, as that would defeat the purpose of the gag. It's a variation of Who Framed Roger Rabbit's Rule of Funny -- Saitama can do anything (or in his case, defeat anyone) as long as it's funny.

9 What is Going on With Adam and Tadashi?

For the first eleven episodes of Sk8 the Infinity, it appeared that Tadashi wanted to help redeem his boss, Adam, who had betrayed his former friends. That all turned on its head during episode #12, when Adam declared that Tadashi would be his "dog," forever. Tadashi seemed delighted at the idea, which made fans run wild. Did he need rescuing from a toxic relationship? Was there some sort of mutual agreement between the two men that even audiences weren't aware of? Hopefully, more answers will be revealed in the upcoming second season.

8 What is the History of One Piece's World?

With over 1,000 episodes since it first aired in 1999, One Piece and Monkey D. Luffy's escapades have captured audiences worldwide. One of the more puzzling aspects of creator Eiichiro Oda's world is its ancient history. Now that the series is entering its Final Saga, audiences may soon get more details. There has been some foreshadowing along the way, including the existence of a futuristic kingdom and the impending destruction of the Red Line. Only with time will more details come to light.

7 Was Johan Liebert Unwanted?

The final episode of 2004's Monster brought Dr. Kenzo Tenma face-to-face with none other than the killer Johan Liebert. Johan revealed, with mere minutes of the anime left to spare, a quandary that had stuck with him all his life. Johan's mother was forced to give up one of her children to the horrific experiments of Kinderheim 511, and she chose Johan's sister, Anna. However, she dressed the twins identically at the time, and it's not clear if she knew who she was giving away. In other words, Johan will never know if he was unwanted or not.

6 What Did Gendo Say to Ritsuko?

There were plenty of unanswered questions in the psychedelic trip that was End of Evangelion, but one of the biggest was what Gendo said when he confronted Ritsuko, the NERV facility falling to pieces around them. Audiences only see him mouth a line, to which Ritsuko replies, simply, "liar." Did he say something that made him worthy of redemption, or something more in line with the person he has shown himself to be throughout the series? Either way, Ritsuko doesn't believe him, and audiences are left only to speculate.

5 Did Spike Spiegel Die?

In Spike's final throwdown with Vicious at the end of Cowboy Bebop, he manages to shoot Vicious in the chest but suffers a katana wound in the process. Spike utters the iconic "Bang!" before he falls, in line with his attitude throughout the series that "whatever happens, happens." Whatever happened, he appears to have embraced the outcome. But did Spike really die in the finale? Series creator Shinichirō Watanabe has been curiously mute on that point.

4 Who is Deku's Father?

The My Hero Academia anime has kept the truth of Deku's parentage a secret for six, going on seven seasons. Many suspected All Might of being Deku's true father, although it seems he is more of a father figure to Deku than anything. My Hero creator Kōhei Horikoshi revealed that Deku's father is named Hisashi Midoriya, though little else is known. Fans are already chomping at the bit to know more about the mysterious Midoriya, Sr. and just what he has been up to during his absence.

3 Who is Ash's Father?

Clearly, anime fathers aren't exactly known for being present, and this is especially true for Ash Ketchum's dad in Pokémon, whose identity remains a mystery. The most popular guess for Ash's father is Professor Oak, who watches out for Ash like a son, but this is in no way certain. According to Ash's mother, Della, he is off on a journey to become a Pokémon master himself. Perhaps Ash will bump into him some day in the midst of his own journey.

2 What Happened in Griffith's Past?

Berserk is elusive when it comes to sharing anything about Griffith's past, and even those details are filtered through Griffith's own eyes. He appears to have grown up in the slums, perhaps as an orphan, with dreams of one day having a castle like the one that shadowed over his town. But is that enough information to whet the appetites of curious audiences, who have imagined all sorts of tragic backstories that made Griffith the ambitious man he is today? Perhaps not, but some would argue that it's even eerier to fill in the blanks. The "not knowing," after all, is part of Griffith's allure.

1 Where is Ice Adolescence?

Ice Adolescence, the much-awaited prequel to 2016's Yuri on Ice, has been in the works for years, with a strange lack of updates. Save for a movie poster and a brief trailer that suggests the film will delve into figure skater Viktor Nikiforov's past, Studio MAPPA has been curiously quiet about the whole project. So much so, in fact, that memes with the very tagline "Where is Ice Adolescence?" have floated around the internet.

It's clear that, with varying levels of seriousness, there are plenty of mysteries still afloat in the anime community. Whether they be more lighthearted or serious there is, and always will be, plenty of discussion fodder to keep fan communities alive. Hopefully, the biggest unsolved mysteries in anime will be answered sooner rather than later.