In the unforgiving vacuum of space, the difference between life and death can boil down to a single bad decision or a millisecond of delay. And when the nearest help is as far away as another planet, the only one you can trust to save you is yourself. This lesson is driven home in the most brutal fashion possible as a series of accidents strand Mutta's brother Hibito and another astronaut on the lunar surface. As Hibito fights to keep his injured companion alive, Mutta must join a team of scientists and fellow astronauts as they struggle to find a way to locate and save their friends before their critical oxygen reserves run out. And if that wasn't enough of a test, Mutta's entry into JAXA training becomes its own ordeal when he and his fellow trainees are dropped into the survival test course on an accelerated schedule. Foraging for food and facing wild animals on one planet, and fighting for one's last breath on its satellite, two brothers worlds apart find common ground in the fight to stay alive in SPACE BROTHERS Collection 4!