You can decide for yourself when something is spiritually bad by these criteria:
- It causes doubt in your heart
- You do not want the people you respect the most to know you are doing it
- When you feel very spiritual (for example if it is Ramadan and you have been reading a lot of Quran) you want to avoid that thing.
The ideal Muslim is the one whose private life and public life are the same so that there is nothing secret in their lives that they would not want others to find out about.
As for your specific question, if the anime has erotic elements, then that is forbidden to watch (as discussed here).
If it is not erotic, homosexual relationships are still obscene (fāḥish) and the Quran says:
and do not come near obscenities, whether outward or inward... (from the Quran, verse 6:151)
Watching a show that celebrates homosexuality is a way of “going near obscenities” which the above verse strongly discourages. Therefore the admirable and pious thing to do is to avoid such shows.
I have a question what about anime fantasies
are anime fantasies (some are sexual)
haram or halal as long as someone doesn’t do it ( he likes to think of it but doesn’t do it )
Well, I don’t know if it’s haram or halal. Not trying to make new rules. But, I think the prophet Mohammed (PBUH) once said that you don’t get bad deeds when you think about evil thoughts and such. As long as you don’t put your thoughts in to action, I think it’s fine. Note: I was talking about thinking of sexual or bad thoughts. And, not sure if it’s prophet Mohammed (PBUH) the one who said that. But, it’s a fact. It’s not considered a sin to think about bad things. Also, again, as long as you don’t put your bad thought in to action, it’s not a sin.
However, if you meant watching anime fantasies that are sexual, and not doing anything while watching, just having bad thoughts, it’s still haram. Watching sexual scenes are considered a fahisha. Meaning, considered soething bad; haram. So, it’s better for you to stop now. It can affect your mindset. Trust me, I have been there. It will become an obsession and will lead you to watch bad scenes in movies, anime, dramas, and etc. Please, try to stop.