Anime is notorious for ambiguous endings. It's one of the main criticisms that most people have for the genre, but whether an ambiguous ending is good or bad is more a question of context and personal taste. Not everyone likes their plot or characters all wrapped up at the end. An open ending that leaves the ultimate fate of the characters in question can work better for the storyline as a whole.
An ambiguous ending is often meant to keep with a tone of a movie that also tells a story that's subjective or philosophical, but sometimes there are more practical reasons for keeping an ending open. Often, it's just a way to keep the opportunity available for sequels, spinoffs, and further development.
8 Ghost In The Shell (1996)
The closing scenes of Ghost In The Shell don't feature the main character Mokoto, nor the entity known as the Puppet Master, but a creation that is a complex amalgamation of the two. The audience only has a vague idea of what this means exactly — and that's the point.
Throughout the course of Ghost In The Shell, the main character is in pursuit of a criminal mind that appears to belong to a master hacker. It turns out, however, that this hacker is actually a sentient AI program searching not only for asylum and understanding but evolution. They succeed, but the ultimate result of their quest is left up to the viewer.
7 Ninja Scroll (1993)
It was intended as a one-off, and it's a great story on its own. The popularity of Ninja Scroll, along with the ambiguous ending, gave rise to sequels and spinoffs in later years. The film has an impressive pedigree, produced through a collaboration with companies like JVC and Toho, and the animation is done by the notorious artists at Madhouse.
The movie plays on and subverts a few interesting adventure tropes, adding some occult thriller and gruesome action to an otherwise dreary story about political power and historic Japan. The final scene is of the protagonist walking off into the horizon, reminiscent of old Westerns.
6 Princess Mononoke (1997)
There are two plots in Princess Mononoke: one about the main characters and the other about the ultimate fate of the larger world in which they live. San has lost her family matriarch, but her siblings remain, Irontown will likely be rebuilt, and Ashitaka's curse has been lifted.
Some of these loose ends are neatly tied up by the movie's conclusion, but the larger question about what the future will bring is never decided. Anyone expecting the hero and his love to ride off into the sunset will be sorely disappointed.
5 The End Of Evangelion (2002)
There are two different endings to the classic Evangelion series, so just to be clear, this is the feature-length film that was considered to be the conclusive end to the anime series that ran from 1995 to 1996. It takes a few re-watches to figure out what's happening in the first place before moving on to the ambiguous conclusion.
The TL;DR of the plot is that, at the end, Shinji gets to choose if humanity evolves as the Human Instrumentality Project intended, as non-corporeal entities. He chooses to stay an individual, and he and fellow Eva pilot Asuka are the first two human beings to return to the physical world. What happens to them after, however, is left totally ambiguous. Even the new movies have yet to fill in that gap.
4 Claymore (2007)
There are only 26 original episodes of this anime, and there needs to be more. Considering there's enough material in the manga series to cover almost 13 years, it's not like the source material isn't there.
In this world, which seems like a parallel universe of pre-industrial Europe, a Claymore is a human-demon hybrid and their purpose is to fight demons. The main character, Claire, is one of these Claymores, and she survives the challenge of these 26 episodes with some big plans for independence and travel. It's never revealed what those are, unfortunately.
3 Nausicaa Of The Valley Of The Wind (1984)
In the spirit of Ghibli movies with a message, the main characters complete their immediate arcs, but the bigger question of their ultimate fate is left ambiguous. Nausicaa, the princess of the Valley of the Wind, succeeds in saving her home and her people from their immediate threats, but what the future holds is uncertain.
The relationship that humanity has with their environment, in this case, toxic sand and aggressive, angry bugs, is definitely better than it was when the movie started. The secret of the Wastelands has been revealed, but it's not a process that will wait for earth's human inhabitants, and it is unclear whether humans will survive it.
2 Berserk (1997)
The ending of the original Berserk was so ambiguous that it really felt more like the series was unfinished. This open ending gave rise to a number of spinoffs and sequels decades later, but for many fans, their head canon ends here.
This is the series that consisted of 25 episodes that were aired in 1997 and 1998. The first episode of this version introduces Guts's post-demonic sacrifice, and the next 24 episodes tell the visceral and sordid story of how he came to be a one-eyed one-handed warrior seeking revenge against the king. What happens afterward, however, is left out entirely, as is the fate of Casca — details that are filled in with the 2016 adaptation.
1 Akira
Akira is a movie that fools the viewer at first. It's presented as an action-adventure thriller with a touch of mafia or crime drama in a cyberpunk setting. Things take a dramatic turn, however, when a member of a local motorcycle gang, named Tetsuo, comes in contact with a mysterious person with psychic powers who seems to have escaped from a government research facility.
What follows are some of the most gruesome and terrifying displays of psychic power that have ever appeared on film. Only the superior power of Akira can stop Tetsuo's psychic rampage. The viewer first assumes that Tetsuo is dead at the end, but the last line of the movie reveals that he's still with us. What exactly that means is left up to the viewer to decide.