OOZ662 said:
Not sure what you're actually asking for. I assume you know you can just add a minus to the beginning of a tag to exclude it. Gold members and above also get +/- buttons next to the list of tags that show up to the left of search results to quickly add and remove tags that are popular in the result from the search (aided by the ability to search for 6/12 terms instead of 2).
Basic users are limited to two tags period, including meta tags (like rating, fave count, etc) so to use -tags, you'd have to sacrifice one of the search tags. It's a roundabout solution, but why not temporarily add the stuff you don't wanna see to your blacklist? To use your example, when you do your twins brother_and_sister, simply add Rin and Len to your blacklist then remove them once you're done.