Love the look on his face at the 13 second mark!!!

is there a tag for whatever the umbreons dick is doing in the sheath? sheath_masturbation?

heha said:
is there a tag for whatever the umbreons dick is doing in the sheath? sheath_masturbation?

Essentially he's becoming partially erect at moments, so it's growing out and shrinking back in. The speed and degree of growth is exaggerated for visual clarity, though I must confess your thought of "sheath masturbation"... It probably does feel good, huh?