Shin

In the manga, Baku's father's true identity is Shin, a powerful warrior from En and his sister's home planet. He uses a Greatsword as a weapon and gave his life to protect his planet's refugees during a war. Shortly after their escape, the enemies who destroyed their planet continue to pursue Shin and the refugees through space. Shin then decides to face them alone, and before dying, he leaves his sword with Princess Amano, so that she can protect herself, En and Baku in the future.