[ Manga XXX ] Youjuu Kyoushitsu 2

Our planet was formerly ruled by Demon Beasts until an ecological cataclysm drove them away 100 million years ago. Now they must mate with human females in order to produce a new, hybrid species that will pave the way for an advancing army of invading creatures. A mutant, lust-driven Demon Beast kidnaps Kayo when she is 19 years old, and it is up to Interplanetary Mutual Observation Agent Muneto, also 19 at the time, to rescue her from the horrible monstrosity to which she gives birth: A mutant, lust-driven Demon Beast!