Japanese animation is notorious for using western/european symbolism and beliefs, such as the cross, religion, and other imagery, words, names, etc, and perverting it in some fashion for the sake of story telling. They might claim they are completely removing any meaning to these objects, but to us, it may be offensive and should be avoided if it’s use is scandalous or given to scandal.
The good news (which is really bad news) is that the japanese tend to make a fetish out of pretty much anything, so you will know visually when something is immoral or presented to you for that purpose because the object may not be bad, but it’s clear they’re abusing it.
We can more or less predict when we will run into sinful material in our anime watching too, since we are more than likely searching for shows by using tags or specific search options, so we are making an active, intentional choice to search for specific things that excite us, and if those specific things always turn out to be sexual or violent, for example, then maybe that says something about the viewer, a sort of self revelation. A change in genre might be in order.
We’re Christians, so we’re called to a higher standard in this area, so I believe that while anime is not a sin in itself, and a show is not necessarily immoral just because it has some fanservice, we have the choice to avoid sinful material when it is present; if we do not, then its a matter of whether the content was grave matter or not; if it was, you would need to confess it, and even if it wasn’t, you might want to confess it anyways if you felt bad about it.
Remember, you can always skip that episode, skip that scene, or fast forward, etc, if you know it disturbs the peace of your soul and conscience. It doesn’t necessarily mean you’d have to stop watching the show alltogether. However, if occasions of sin for you keep coming up with the show, it might be an indication that you need to choose a different show. I’ll admit, it’s not always easy giving up on an otherwise good show for spiritual, moral, and religious reasons, but you feel good about doing the right thing afterwards.
Anime, like many other forms of entertainment, can desensitize you to the immorality and sinful content within it. Just because something doesn’t make you feel “turned on” in the case of ecchi or harem type shows, for example, doesn’t mean it’s necessarily good for you to watch it anyways, or overly bloody, gory, type shows just because it doesn’t make you crave violence. While there may not be a physical stirring in the body that causes sin, consider that the mind is at work subconsciously and that spiritually we may become weaker by choosing to predispose ourselves to such content.
If you’re watching a show for the first time, I would say analyze the general themes and if you see a repeating pattern of immorality, then you’re probably watching something you shouldn’t.
Incidentally, shows like Bleach, Naruto, etc, are so generalized in the genres they cater to that they don’t overextend in any one thing, and this generally makes them safe to watch, because they’re not devoting large sums of time to something perverted, overly violent, etc. Alot of these sleeper hits that hit the summer, fall, and winter seasons are the ones to look out for, as they are usually ripe with immorality of some kind.
In the end, it’s a judgment call that requires prudence and discernment if you plan to watch the show. After a few episodes you should pretty much be able to tell what they’re trying to sell you. You’ve got to just take it from there. I hope this helps. God bless.