Second season.

In the distant future, trains are no longer bound by their physical tracks. Instead, they take to the skies and travel across the universe on the Galaxy Railways, transporting mankind from planet to planet. However, the Galaxy Railways are no safer than traditional trains: criminals, terrorists, and vile aliens always find a way to stir up trouble. Manabu Yuuki, a rash and hot-headed man, is the latest addition to the Galaxy Railways' elite Space Defence Force (SDF). These brave men and women are responsible for protecting the railways and responding to any unprecedented danger, risking their lives to protect the innocent from evil. But as this drama unfolds and the SDF's greatest crisis draws nearer, Manabu must truly learn what it means to be a member of the SDF before it is too late. [Written by MAL Rewrite]

In the distant future, trains are no longer bound by their physical tracks. Instead, they take to the skies and travel across the universe on the Galaxy Railways, transporting mankind from planet to planet. However, the Galaxy Railways are no safer than traditional trains: criminals, terrorists, and vile aliens always find a way to stir up trouble. Manabu Yuuki, a rash and hot-headed man, is the latest addition to the Galaxy Railways' elite Space Defence Force (SDF). These brave men and women are responsible for protecting the railways and responding to any unprecedented danger, risking their lives to protect the innocent from evil. But as this drama unfolds and the SDF's greatest crisis draws nearer, Manabu must truly learn what it means to be a member of the SDF before it is too late. [Written by MAL Rewrite]

During her summer holiday at her grandparents house Tamai Shiina, a young and cheerful schoolgirl, meets a strange looking creature. They befriend each other and Shiina names it "Hoshimaru: The Round Star." When Shiina returns home after the summer to go back to school, she starts meeting other kids that also have befriended a strange creature like Hoshimaru. But she soon finds out that not all these creatures and their masters are as friendly as Hoshimaru. (Source: ANN)