I would like to implement a blacklistable underage sex tag...I'm not here to judge peoples fetishes but its a real pain for my eyes when i come across pictures with underage sex and can't find a way to blacklist them.

The close related tag is *young* but if i blacklist this one, i lose sight on pictures with characters that look under 18-25 ish years old as well.

I don't even know why these kind of pictures are even legal here but this is off-topic.

All lines on the blacklist are considered separately, so the correct solution is "young sex" on one line.

If young sex is producing too many false positives you can try cub sex which is typically used for even younger characters.

I had it blacklisted myself but people seem to apply the tag so liberally and inconsistently (especially to chibi stuff) that I'd be navigating a pool and halfway through the comic I'd encounter a blacklisted page for no good reason.

One refinement would be to blacklist "young sex -teenager" to keep in some (admittedly not most) of the older young content. I think a "prepubescent" tag would be useful. Its' easier to judge and seems more useful than "child" or "teenager" which are based on ages 3-12 and 13-19.

Edit: alternatively you could blacklist "baby, toddler, child, cub, loli, shota" on separate lines which would in theory catch the younger end of the spectrum, but in practice those tags aren't as widespread as the probably should be, likely because of the ambiguity in precise ages.