Anime falls into the category of entertainment. When wondering whether a movie, tv show, or any piece of entertainment is haram to to view, then simply put, if it contains or promote haram then one should avoid it.
One shouldn't view that piece of entertainment when:
Use these answers and the best of your rationality to decide if a piece of entertainment is worth viewing. If you're doubtful then it is good to avoid doubt but at the same time, don't overthink it.
Sunan an-Nasa'i 5711 (Sahih)
"I said to Al-Hasan bin 'Ali, may Allah be pleased with him: 'What did you memorize from the Messenger of Allah [SAW]?' He said: I memorized from him: 'Leave that which makes you doubt for that which does not make you doubt.'"