You were on a ship, with other two girls, and guess what? The ship was infestated with aliens, so, now you three will have to fight for survival!

you three are reunited in a safe place of the ship

Kouhai: "Man... This whole thing sucks..."

Senpai: "Kouhai, I know, we all want to get out of here... These aliens are really annoying... They try to abuse us two, and they're violent to any other men... I wish we could go back home as soon as possible..."