Gamon Sakurai, author of the hugely popular sci-fi manga Ajin, hits us with an all-new sci-fi thriller! Dropped thirty miles from home base on an alien planet, Chief Yugi Oishi must lead her men and the exploratory excavation crew they find stranded in an abandoned mine to safety as alien monsters close in on them from both sides. But not all is what it seems, and there may be more than one danger lurking in the dark.

Twenty years ago, a wormhole suddenly appeared above Earth's orbit and opened a passageway to an alien planet full of untapped resources and mysterious life forms. Two decades later, Team Sierra, a small military squad of security specialists working for the Tiberius Coke Corporation, are thirty miles away from home base on that planet when their leader, Chief Yugi Oishi, spots an SOS flare coming from a theoretically abandoned mine. Despite the danger, she leads her four-man team to the facility to see who'd called for help, only for it to be attacked by a horde of powerful creatures almost as soon as the doors close behind them. Now, she and the stranded exploratory excavation crew Team Sierra finds inside must traverse the treacherous mine to reach the only vehicle that could get them to safety—without waking the terrifying monster that's been picking off the researchers one by one.