A size shifting demon who is tricked and enslaved my Midori.

Episode 1: A young man named Norikazu finds a computer from World War II buried in his back garden. When he activates it, he and a girl named Midori are transported to Hell where erotic creatures and monsters of different kinds live. They meet some friends including a sexy elf type woman named Eganko who falls in love with Norikazu, and a perverted monster prince who is soon enslaved by Midori. Using their new friends the pair try to make the dangerous journey back home. 
Episode 2: Having made their way back home the adventure duo find the world they knew is gone, and is now ruled by the demonic computer which first sent them to Hell. They travel back in time to World War II Japan in an attempt to stop the world from being changed. Notably, in doing so they witness the atomic bomb being dropped on Hiroshima, and there is an appearance of the Enola Gay, as well as numerous symbols of Japanese culture at the time. 
Episode 3: This episode has a humorous love-quadrangle plot, where Eganko comes up with a plan to make Norikazu fall in love with her with a love potion, and simultaneously make Midori fall in love with an egotistical young man from her school. Unsurprisingly their plan backfires and everyone gets what they deserve. 
(Source: Wikipedia)

Kingan