Tadatos Lane, known as Tada, is an orphan from Terra who grew up on Sibberies. He possesses esper abilities, including the power to detect truthfulness in others, a skill that proves crucial during group dynamics. As a candidate for the elite Cosmo Academy, he undertakes the final examination: a survival test aboard the derelict spaceship Esperanza alongside nine other applicants. The sudden appearance of an eleventh member immediately sparks suspicion and tension.

Tada's unexpected knowledge of the Esperanza's systems initially casts him as the prime suspect for sabotage, as his insights baffle the others. This suspicion deepens as unexplained malfunctions and crises unfold. His background later clarifies his familiarity; he is a survivor of the disaster that crippled the Esperanza 120 years earlier, having been rescued as a child from suspended animation.

Throughout the test, Tada emerges as a leader committed to group cohesion. He champions cooperation despite rising paranoia and actively tackles life-threatening problems, including the ship's decaying orbit and a spreading illness. His bond with Frolbericheri Frol becomes central, especially when Frol contracts the illness. Tada supports Frol's wish to avoid mandatory womanhood under their planet's patriarchal system, even offering marriage should Frol fail the exam.

In the climax, Tada demands activation of the emergency beacon to save Frol's life, placing survival above passing the test. Supported by the group, this action underscores his values. Following their successful rescue and passage of the exam, Tada and Frol become pilots and eventually marry.