Plot
In the year AD 2225, mankind has expanded from Earth to inhabit nearly all the planets and nearby moons in colonies and settlements. Space travel has advanced to the point of being commonplace; for the inhabitants of the Solar System, becoming an astronaut is a realistic career path. One of the schools established to train future space voyagers is the Liebe Delta, a space station positioned in Earth's orbit. This progress exists despite the Geduld, a mysterious sea of plasma that erupted from the sun along Earth's orbital plane in AD 2137. Stretching from the sun to the edge of the solar system, this phenomenon of high temperatures and gravity pressures remains unexplained.
Kouji Aiba, a sixteen-year-old boy, leaves his home on Earth to attend the Liebe Delta and train for his Level 2 piloting license, traveling alongside his childhood friend, Aoi Housen, who unexpectedly reveals her enrollment in the station's flight attendant program and informs him that his younger brother, Yuki, will also be joining the same flight class.
The students and teaching staff on the Liebe Delta lead normal lives, focused on their studies and daily routines. They even have a vacation period, called the Dive Break, during which the space station approaches the Geduld for system maintenance. Out of approximately 1,000 students, about 500 remain onboard during the break. Unknown to everyone, the space station is sabotaged by a gas attack during a routine dive, leaving most of the staff unconscious. The Liebe Delta begins free falling into the depths of the Geduld Sea, where the intense gravitational pressures threaten to crush the station and kill everyone aboard. The remaining instructors sacrifice their lives to save the students, but their efforts fail. Just as the station teeters on the edge of collapse, a hidden ship called the RYVIUS activates and surfaces from the Geduld Sea, rescuing the surviving students aboard the Liebe Delta.
Now stranded in space and abandoned by humanity's governments, the students aboard the RYVIUS must navigate their new reality. As anger, fear, and tension grow among the crew, Kouji struggles to maintain order and unity. He faces personal challenges (including clashes with his brother Yuki), his complicated feelings for the Uranian aristocrat Fina S. Shinozaki, the task of avoiding Aoi, and the mysterious appearance of a girl in pink wandering the halls. As the situation worsens, Kouji must determine whether he can guide the RYVIUS to safety or if he will lose everything he holds dear.
Main characters
- Kouji Aiba – The series’ primary protagonist. A diplomatic and empathetic student who repeatedly attempts to maintain social order aboard the Ryvius, ultimately helping guide the castaways back toward cooperation and civilian norms.
- Yuki Aiba – Kouji's younger brother and one of the most skilled pilots aboard the Ryvius. His emotional isolation, rivalry with Kouji, and role as a Vital Guarder operator place him at the center of the ship's power struggles.
- Aoi Housen – A childhood friend of the Aiba brothers and a flight attendant trainee. She serves as an emotional anchor for the group and plays a key role in resolving interpersonal conflicts.
- Ikumi Oze – A charismatic and talented pilot who later becomes one of the Ryvius's captains. His traumatic past and growing paranoia lead him toward increasingly authoritarian rule.
- Airs Blue – Leader of Team Blue and an early captain of the Ryvius. He represents violent authoritarianism and introduces the controversial points system that deepens divisions among the crew.
- Juli Bahana – A senior student and de facto leader of the elite Zwei. After Team Blue's fall, she assumes command and represents a restrained, ethically motivated alternative to previous regimes.
- Stein Heigar – A calculating strategist among the Zwei whose pursuit of order evolves into a harsh technocratic rule, highlighting the dangers of control-driven governance.
- Neya – The biological core and guardian entity of the Ryvius. An enigmatic non-human being whose interventions are crucial to the survival of the ship and its crew.
