@Osamu09
One of the risks of using transliterated Japanese words as tags, not everyone will know what they mean. Having an actual English translation or term as part of the tag (with one of those | dividers) would avoid this sort of confusion. After all, a good number of people who see a tag that is a word they don’t know are just going to ignore it, not enter it into the search bar or click on it to load the search page that lists the definition.
as many perople already already pointed out in other suggestions, the "inseki" tag exists, which is non-blood related incest (such as step-sister, mother in law, etc.)
also I checked the example and there's actually a simple explanation for it. Most people don't know about the inseki tag. If you look carefully the "incest" tag has been added by the community. Most of the time the "inseki" tag is already there