Humankind abandoned Earth as it entered another ice age. Over time, those who came to hold dominion over the world were... rabbits!?
After humanity left, the rabbits referred to humans as "giants" and revered the massive ruins left behind as "Smokestack Mountain." Those fearless enough to violate and excavate this sacred site are known as "rust diggers." The protagonist, an old rabbit named Stamp, is one such rust digger, making a daily routine of excavating Smokestack Mountain.

One day, on his way back from exploring Smokestack Mountain, Stamp encounters a rust digging team known as the "BBs" and ends up joining them in a quest to delve deeper into the heart of Smokestack Mountain.

Along the way, Stamp discovers records from ancient information storage devices called "D-TAMs" scattered throughout the ruins. One of these records appears to belong to his estranged daughter, hinting at her peril and revealing hidden truths about the world he once believed in.

To unravel many mysteries and follow his daughter's trail, Stamp continues his journey into the depths of the ruins...

• Mysterious setting
  Experience exhilarating action and mystery as you dig ever deeper into the giant ruins!

• "Smash and Dash" your way through mazelike ruins
  With your mech's ninja-like speed and mobility, explore the ruins by smashing through blocks, and loot any treasure that awaits!

• RPG-like progression and customization
  Upgrade your mech with parts and materials collected from within the ruins! Improve Stamp's skills through intense battles with enemies guarding treasures!