Dowajwo!

Tommy is on the verge of being expelled after failing his graduation exam several times. He must pass this exam no matter what, but the monster he must defeat, Murtung, likes human bodily fluids the most...? While trying to escape from the creepy Murtung attack that is closing in on him, Tommy gets stuck in a wall, and a troublemaker at school named Pestle Big, who happens to be passing by, offers to help him pass the exam if he sucks his member just once. Graduation or chastity? Tommy stands at a crossroads in his life...

(Source: Lezhin, translated)