Hacchake Ayayo-san 5 - Pikapika no Shouwakusei - Ayayo's Dive Aframe

Ayayo, Tomoko, and two other female friends travel on a spaceship to another planet. However, they are abducted by an alien race ruled by a king with bizarre sexual preferences. The remainder of the plot is dedicated to exotic sexual scenes between the girls and the aliens.

[From Moby Games]