If you liked
Ansatsu Kyoushitsu
|
...then you might like
Boku no Hero Academia
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Both are similar in that they both feature a class taught by an outstanding teacher (All Might/Koro-sensei) with an objective goal in mind. In My Hero Academia, it's all about becoming heroes. In Assassination Classroom, it's all about becoming assassins. Even the main characters are similar: Nagisa and Izuku both wanting to aspire to be like their teachers, violent geniuses Karma and Bakugou, and the cheerful, hardworking Kayano and Uraraka.
If you liked
Ouran Koukou Host Club
|
...then you might like
Akatsuki no Yona
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This is a bit of a stretch but I'd recommend AkaYona if you liked OHSHC. Both main characters are strong female leads who want to stand up for themselves. However, they are surrounded by a group of males who want to do nothing more than to protect them. However both main characters are stubborn, and refuse to let the guys do everything for them. The males are hesitant, but they are happy to comply, and respect them and their decisions.
If you liked
Lucky☆Star
|
...then you might like
Watashi ga Motenai no wa Dou Kangaetemo Omaera ga Warui!
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Both main characters are very alike, as in they're both otaku and have similiar interests. However while Watamote looks at the downsides of being an otaku (and perhaps the reality of it for some), Lucky Star has a more optimistic view on what it means to be an otaku. I'd recommend watching both to really compare the unhealthy otaku Tomoko vs healthy otaku Konata.
If you liked
Majo no Takkyuubin
|
...then you might like
Little Witch Academia
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- both main characters are excited to become "real witches" - both main characters start off optimistic, but later face oppostion from others about being a witch / personal views on being a witch - both main characters have to learn a thing or two about independence and face reality
If you liked
Black Lagoon
|
...then you might like
Gangsta.
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- both the Lagoon Company and Benriya are NEUTRAL parties in the story - criminals, gangs, drugs and violence - in a setting where crime is prevalent (and normal) - diverse cast - (many) characters with tragic pasts - carry a similar "vibe"