I'm confused... Your tag description is describing voyeurism, a tag which already exists. However the tag name is the english word for netorase, which again is a tag that already exists.
"netorase" is the closest thing, but it implies that the characters is/was in a relationship with one of the characters involved in the sex. If there was no relationship then "voyeurism" would be close as well, but it implies the character is hiding from the people involved, but if he's not hiding then I think it would count as "exhibitionism" which would be a much broader tag though. Overall the suggestion is fair, though some examples are needed