The episode begins with first-grader Umika Konohoshi reflecting on her newfound friendship with Yu Akeuchi, an alien classmate. Umika is determined to build a rocket to fulfill their shared dream of reaching space. However, she quickly realizes that constructing a real rocket is a daunting task.

During class, Umika worries about how to protect Yu’s secret hideout in an abandoned lighthouse. Her classmate Haruno Takaragi, the deputy class representative, brings up the lighthouse, which unsettles Umika. She fears that Yu might be captured and dissected if people learn about his secret base. Umika tries to divert attention away from the lighthouse, and Haruno eventually drops the subject.

Later, Haruno joins Umika and Yu, expressing her enthusiasm for their spacefaring ambitions. She becomes part of their team, and the trio decides to start small by building a rocket out of soda bottles. They gather materials, including soda bottles, and begin construction. Umika demonstrates her crafting skills, while Yu adds her unique flair to the design.

The group decides to launch their finished rocket from the lighthouse. Haruno suggests that the lighthouse would be an ideal launch site, and everyone agrees. Upon arriving at the lighthouse, they set up the rocket on a makeshift launchpad. Umika explains that while the rocket will fly due to air pressure, it won’t reach space. Yu is relieved and admits that she’s still unsure of her origins and is happy to stay on Earth for now.

Haruno asks Umika what she would do if she encountered aliens in space. Umika expresses her desire to escape Earth’s problems and befriend the aliens. Haruno, on the other hand, wants to show the aliens the beauty of Earth. This conversation leaves a lasting impression on Umika.

Finally, the moment arrives. The trio counts down and launches the soda bottle rocket. It soars into the sky, creating a moment of joy and unity among them. The rocket lands in the sea, but the experience leaves them all exhilarated.

The episode ends with the three friends looking forward to the next steps in their shared dream of space exploration, setting the stage for the next episode titled "Explosive Mechanics."