The Endless Frontier is a collection of multiple worlds connected by dimensional portals known as "Cross Gates". In one of these worlds, Bounty Hunter and amateur ladies man Haken Browning and his Artificial Human Sidekick Aschen Brodel explore the ruins of a crashed spaceship, one they were both found in when Haken was just a baby. Inside they find, much to their surprise, a rather well-stacked young woman with a big-ass sword and a tiny dress sleeping in the crew's quarters. Turns out she's Kaguya Nanbu, The Ojou of one of the Frontier's worlds. Upon finding out there's a reward for her safe return, the pair decide to accompany her home. Since this is roughly the first ten minutes of the game, things naturally start to snowball from there: strange crystals start sprouting up all over the