SPACE BROTHERS

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.

The third exam will take two weeks. Mutta and the other candidates are transported via sealed bus to a large, barren facility. Then they are led to an area that is known as the last room.

The fifteen remaining candidates have been divided into three teams of five. Each team will spend two weeks inside a sealed box, while completing various tasks. The first task is to determine the time.