It was their final test before employment at a certain space development company...
Izumi and John experience some trouble with their small spacecraft, and it collides with a rather large vessel. In order to free their own ship, the pair has to board the larger one... which turns out to be the Todoroki, a craft used for secret experiments.
Anyone who comes into contact with "Mysterious Being X" will require 3 injections to ward off its influence. Luckily Izumi has one, but to find the other two, the pair will need to explore the Todoroki thoroughly. But a side effect of the injections is that Izumi starts to get hornier...