It's not a dick nipple, it's an enlarged nipple. (The futanari girl is doing medical experiments, one of the pills gives her a cock, the other pill has different effects depending on who takes it. In the dark blue haired girl's case, it gives her massive nipples and make them extra sensitive.)
...so both nipples are enlarged, it's just you can tell because the futanari girl's arm is in the way.
Btw, I was curious how long it'd probably take, till someone posts a comment about UB not being a legit source. Confirmed answer: 1 hour. That's a new record. Congrats!
