The character on the right has been in a bit of a flux and caused a few wild tag edits and forum threads.
The character is male-to-female, with a penis. The artist has stated the character identifies as male.
However, 99% of the time we tag based on what we see. If someone searches yaoi and gets the formerly-tagged-yaoi pic of this character giving paizuri, it's not gender politics, it's tag poisoning. Same goes for whoever keeps tagging them as newhalf even when you can't see their dong.
If there's clear evidence of them being trans, such as everyone's favorite catperson (post #4017882) or clearly showing them transitioning (post #2646299), then you use the transgender tag, not futanari.