Hekigan no Soukishi Feril to Ririka

The main character is the boss of an evil group. He has just destroyed all the elf tribes and is now trying to attack the human tribes. But there are Feril and Ririka, who are survived elves, in one of the human tribes and they counterattack to take revenge on them. After a long battle, he successfully captures Feril and Ririka.... But he gets injured at the same time. To cure it, he needs hi-quality energy. The main character transforms himself into a monster and sexually assaults the two elves. As they are raped by ugly monsters one by one, they gradually get addicted to it....