Demon Beast Invasion (1990) +18

Original title: 妖獣教室

100 million years ago, an ecological disaster drove the Demon Beasts from our world. Now they must breed with human females to create a new, hybrid creature who will clear the way for an invading horde. When 19-year-old Kayo is raped by a possessed lover, it's up to 19-year-old Interplanetary Mutual Observation Agent Muneto to save her from the terrifying creature to which she gives birth: A mutant, lust-driven Demon Beast!