It's a group sex act that does not exclusively involve females. If there were several pairs or smaller groups, and some were female-only, then there may be an argument, but this picture is a singular endeavor by all involved.
Personally I dislike the absoluteness of the "futa isn't yuri" standard; there are other images on danbooru where purely lesbian acts are going on in addition to futa goings-on. But a mod or janitor will likely take it upon themselves to remove it. Just giving fair warning.
While I gather most futa fans wouldn't mind a bit of yuri sneaking into their tag search results, I doubt people searching strictly for yuri would appreciate the opposite.
Jasper said: While I gather most futa fans wouldn't mind a bit of yuri sneaking into their tag search results, I doubt people searching strictly for yuri would appreciate the opposite.
