Akiho Tanemura is a living superweapon from another planet, created for combat. An unspecified event caused complete memory loss, leaving her unable to fulfill her purpose and rendering the weapon system inactive. Following this deactivation, she was dispatched to Earth as part of Princess Mayuka's mission to recharge the dormant Ultimate Weapon. On Earth, she integrated into the Yoshizumi household, posing as the family's "secret child." Her known background is limited to her origins as a planetary weapon and her displacement to Earth.

She possesses distinctive red hair and green eyes. Her personality is energetic and intensely food-motivated, marked by significant enthusiasm for eating. To activate her latent capabilities as the Ultimate Weapon, she requires exposure to "primitive stimulation," though the specifics of this process remain undefined. Her given name, Akiho (秋帆), combines "autumn" (秋) and "sail" (帆); her surname, Tanemura (種村), means "seed village."

Documented information presents her core narrative function as an amnesiac superweapon navigating a civilian life within the Yoshizumi family.