Happy End no Kyuuseishu

Nao is a college student who draws indie ero-manga. The morning after a grueling deadline crunch, he finds a little snakey boi, which invites itself inside his room. During a nap, it starts sucking on Nao's willy and gulping down the seed... and of course Yasu, Nao's kouhai, walks in. Dismayed as he is by Nao deciding to keep the tentacle as a drawing assistant and manga inspiration, Yasu lets Nao use his hand to jerk off every time it's time to feed the now-named "Wiggle-michi" its semen.

Truthfully, Yasu has always had a crush on Nao. Could this sentient tentacle be their cupid?!

(Source: Gentosha Comics, translated)