If you're looking for manga similar to Interplanetary Intercourse, you might like these titles.
Kei was known as a cry-baby when he was a kid, but luckily he had his best friend, Honoka, who would magic away his sadness using an hour-glass. Now that he is no longer a child, Kei and Honoka’s relationship is being tested as they grow apart. Then one day, the world as we know it is changed by a UFO that visits earth, calling for volunteers to join them. With the world in an uproar, what will happen to Kei and Honoka’s relationship?
School trips are always fun, but they get even better when you're taken to an alien planet you've never visited before. However, this planet isn't exactly safe for a bunch of human students...
Adults--they just don't get the pressures of being babies! Thoughts on growing up from the Kindergarten of Evil students.
16-year-old Gizagaki Fuji always had a temper and hated the idea of romance. A shooting star suddenly crashed into him and now he's become an alien's spaceship?!
Marko is a young Russian university student who is looking forward to finishing school so he can spend more time with his fiancée. However, those plans go out the window when he’s abducted by aliens! These extraterrestrials have a mission for Marko, one that will take ten years. All Marko can do is make the most of it and get to know the strange creatures who are now his co-workers in this offbeat tale of a life far from Earth.