If you liked
Death Note
|
...then you might like
Yakusoku no Neverland
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Both of these manga are WSJ manga in which the main characters try to outwit their enemies and evade capture. They're also both tagged as mysteries on this website, and they both contain content that wouldn't be out of place in a seinen.
If you liked
Tiger & Bunny
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...then you might like
Boku no Hero Academia
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Both anime feature a society in which superhumans are quite common. However, Hero Academia has most people in the world have superpowers, whereas Tiger & Bunny only has some individuals have superpowers. Both anime seem to draw heavy inspiration from western superhero comics by the likes of Marvel and DC, with some very American-looking designs for some characters. Hero Academia focuses on a boy trying to become a superhero, but Tiger & Bunny goes down a different route, with its protagonist being a middle-aged superhero and has a major focus on commercialization of superheroes. If you like the idea of an anime about superhumans in society, both are worth watching.
If you liked
Gintama
|
...then you might like
Kono Subarashii Sekai ni Shukufuku wo!
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Both anime are hilarious parodies, and both have 'trollish' main characters that make their respective anime funny. They both have action, too. Also, both anime have masochistic female characters.
If you liked
Darker than Black: Kuro no Keiyakusha
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...then you might like
Dimension W
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Both have a somewhat sci-fi setting (though DtB is more fantasy-like), and both have a main character who uses wires to fight. They're also both fairly dark and are both seinen. Also, the character designer for DtB created the manga of Dimension W.
If you liked
Inferno Cop
|
...then you might like
Ninja Slayer From Animation
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Trigger made both of these anime, and both are works of satire that deliberately use horrible animation. They also have stupid dialogue and catchphrases ('YEEEART!', 'NANI?!', etc.) Both anime are named after their protagonists, and both are pretty damn funny. Well, only if you like the kind of humour they use, anyway. Also, Ninja Slayer has an awesome dub, but Inferno Cop is dubless (is that a word?). Like Inferno Cop? You'll like Ninja Slayer. Like Ninja Slayer? You'll like Inferno Cop. Simple..
If you liked
JoJo no Kimyou na Bouken (TV)
|
...then you might like
Ushio to Tora (TV)
|
While the manga of JoJo is seen as one of the forefathers of standard battle manga/anime, Ushio to Tora's manga is seen as one of the forefathers of youkai battle manga/anime. Both of these anime have an old-school feel to them and are re-adaptations of manga that got sub-par OVAs years ago. Also, they both have great action scenes and can get a bit brutal at times (JoJo especially). Both anime should be watched before other mainstream shounen because they have influenced those mainstream shounen. At least, that's what I think.
If you liked
Death Note
|
...then you might like
Platinum End
|
Both of these manga come from the same writer/artist combo (who also made Bakuman), and both have a somewhat dark tone. Both manga have supernatural beings (a shinigami in DN, an angel in PE) that give the protagonist their powers (arrows and wings in PE, the Death Note in DE) and follow them around. Also, the protagonists of both series are aiming to become God.
If you liked
Nichijou
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...then you might like
Plastic Neesan
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Nichijou is like a cuter, slightly calmer version of Plastic Neesan; Plastic Neesan is like Nichijou on crack. Both anime use a school setting for a lot of their scenes, and both anime are hilarious. Also, both have girls as their main characters.
If you liked
Mahou Shoujo Madoka★Magica
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...then you might like
Gakkougurashi!
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Both anime seem kind of cute, then change quite drastically at a certain point. Honestly, I can't really say much without using spoilers, but if you liked either of these anime, you might like the other.
If you liked
Binbougami ga!
|
...then you might like
Gekkan Shoujo Nozaki-kun
|
Both are comedies with a focus on parody, and they are also hilarious. Binbougami focuses more on supernatural stuff, while Nozaki-kun is about shoujo manga. Also, Binbougami has a lot more reference-based humour, whereas Nozaki-kun parodies classic anime and manga tropes. If you thought either of these two anime were funny, you'll probably enjoy the other just as much.