The protagonist, a high school girl named Uminoseika (played by Satou Kisei), struggles with extreme social anxiety and has difficulty communicating with others. She is troubled by her inability to make friends and harbors a complex about her personality. “I am not understood on Earth. I’ll go to space to find my place.” While holding onto such fantasies every day, she can't hide her anxiety and attends the entrance ceremony of her high school, where she meets a mysterious new student, Uai Yuu (played by Itou Momoka), who self-identifies as an 'alien'. Surprised to see the alien she had dreamed about suddenly appear before her, Seika musters her courage to speak to Yuu. Upon asking, she learns that Yuu has lost her memory and is looking for a way to return to her home planet. “If we aim for space together, does that mean it’s a win-win?” With the common goal of Seika wanting to go to space and Yuu wanting to return home, the two decide to combine their efforts to build a rocket...! This epic yet delicate story of “Blue” follows the shy protagonist as she grows and strives towards her dreams, sparked by her encounter with the self-proclaimed alien.