Heretical Tentacles, the Sins of a Father and Son

A father and son move to the countryside after losing their jobs and honor. The father, who does not fit in with his surroundings, feels trapped, but his son picks up a creature he has never seen before.
The father observes the tentacle, which repeatedly performs suspicious acts on his sleeping son at night, but the villagers find the tentacle and kill it, claiming that it is a messenger of an evil god. Then the parent's tentacle appears, knocks down the villagers, and begins tearing the son's clothes...

The father masturbates, lusting after his son, who is pregnant with a monster.
As the sperm splatters on his son's body, inside his belly goes bobbing around, and the father realizes something.
"The tentacle wants my sperm"

Official English:
DLsite, FANZA