Implicating butt_from_front → thigh_gap
Link to implication

Reason:

Seems simple enough.

EDIT: The tag implication butt_from_front -> thigh_gap (forum #264916) has been rejected by @NotMeNotYou.

thigh_gap says Images or animations depicting a character, typically female, who is shaped in such a way that even when they are [b]standing with their legs together[/b], a small gap forms between their legs just below their pelvis.

Butt_from_front has a LOT of pictures where the legs are not together. I would actually argue a majority of them are not "with legs together"

-1, SnowWolf already covered most of it, but thigh_gap requires that the legs are closed while butt_from_front can have the legs open or closed. Also it can't work flipped around because sometimes there's a thigh_gap but you cannot always see the butt_from_front whenever there is a thigh gap. It depends on how it is drawn. Not to mention thigh_gap can be from front view OR rear view, while butt_from_front has to only be viewed from the front.

So although there's certainly images that need both, there's too many ways that it breaks and wouldn't work for applying to all of them.

The tag implication butt_from_front -> thigh_gap (forum #264916) has been rejected by @NotMeNotYou.