Half-human, half-monster boys. Though they can take on similar species to that of monster girls, they tend to be depicted less attractive or more on the "monstrous" side of the scale.
Common Monster Boys:
Uncommon Monster Boys:
(Keep in mind, some monster girl species such as harpies or lamias can have male examples, as they might be built on the same concept but have no male equivalent word.)
Do not tag Animal-eared boys, such as cat boys or bunnyboys, or specific types like demon boys. Do not confuse with the monster tag.
The following tags implicate this tag: slime_guy and merman (learn more).