Gorô Saruwatari, a Japanese mountain climber, scales formidable peaks alongside partner Jack "Lostman" Woodbridge. Observing the International Space Station from Everest sparks their ambitions to become astronauts. Saruwatari pursues a civilian path, first gaining hands-on experience as a construction worker specializing in high-risk environments. His critical skills prove vital when he successfully rescues a trapped coworker, preventing structural failure.

Facing delays in Japan's H-3 rocket program, Saruwatari travels to Russia, training and flying aboard the Gagarin space shuttle to reach the International Space Station. There, he contributes to constructing the Horner cargo vessel, part of the multinational "Nexus" program designed for Earth-Moon transport to access lunar helium-3. Saruwatari also participates in testing the Japanese Moon Walker mecha for lunar exploration. An underwater test of this technology results in a fatal accident crushing a diver; subsequent investigations uncover data manipulation and corruption scandals linked to the Moon Walker's development.

In the second season, Saruwatari works with the International Space Agency on the crewed cislunar spacecraft Galileo, aiding its construction. During a critical mission to retrieve a detached solar panel during Galileo's assembly, he unexpectedly discovers a long-lost cosmonaut from a 1969 lunar expedition attempt.

Saruwatari maintains contact with romantic interest Riyoko Ikeuchi through infrequent transmissions during his space missions. His family includes sister Akemi Saruwatari and Yukiko Dianne Saruwatari, who married Mamoru Takeuchi and resides in California.

Saruwatari's rivalry with Lostman persists as they pursue separate paths to the Moon: Saruwatari through international civilian cooperation, Lostman via U.S. military programs. They reflect on each other's progress but have no direct interaction in space during these events; Saruwatari remains unaware of Lostman's concurrent space activities until later.