Space Brothers

The year 2006. Two brothers, Nanba Mutta (age 12) and Hibito (age 9), happen to spot a UFO headed for the moon. The experience inspires them to make a certain promise.

With his mother's assistance and Hibito's encouragement, Mutta has been accepted for the New Astronaut Selection Exam. However, unsure of his next step, he visits Sharon, who works at a nearby observatory. After receiving advice from Sharon, Mutta is finally able to make up his mind.

After advancing to the second exam, Mutta realizes that the other applicants are much better prepared than he is. Desperate to prove himself, he stakes everything on the lung capacity test, as he has confidence in his trumpet-trained lungs. However, as the other applicants drop out, he finds himself in a heated battle with Itou Serika. Who will come out on top?

After a long week, only the final interview remains in the second JAXA exam. Mutta is drawing attention as Nanba Hibito's older brother, but he insists he won't spend his entire life as Nanba Hibito's big brother.

After completing the second JAXA exam, Hibito invites Mutta for a free trip to Houston, Texas, through NASA's family support program. Upon arrival, he finds himself chased by a pug named Apo, and is then reunited with Hibito. However, Hibito expresses disappointment.

Mutta has arrived in America, but he's off to a rocky start with Hibito. Meanwhile, his future as an astronaut is in jeopardy because the headbutt incident has been brought to JAXA's attention.

After learning that his former boss has told JAXA about the headbutt incident, Mutta has given up hope on passing the exam. To cope, Mutta falls back on his childhood habit of multitasking like crazy when something bad happens.

When the robber known as the fire extinguisher man strikes the restaurant where Mutta is, he's in trouble. But once the dust settles, Mutta has become a national hero for capturing the criminal. However, it appears there's more to the story.

After passing the second JAXA exam, Mutta returns to Japan for the third. He's happy about the exam result, but on the flight back, a nightmare leaves him rattled. This is due to the letters from Hibito that he discovered before leaving.

Mutta has learned that Kenji and Serika have strong reasons to become astronauts, while Mutta is simply trying to achieve a childhood dream. This causes Mutta to begin to question himself.