Akina Nanamura, a childhood friend of Kazuto Tokino, resides near his bathhouse and regularly visits him. She harbors unexpressed romantic feelings for Kazuto but ultimately accepts his developing relationship and planned marriage to Princess Valkyrie, despite her lingering regrets. Akina wields spiritual abilities, including barrier creation and demon-ward attacks. After Hydra—a princess from planet Valhalla—crash-landed at her family’s shrine and caused destruction, Akina sealed Hydra’s powers, reducing her to a childlike form.

Akina exhibits acute self-consciousness about her breast size, enduring frequent mockery from Hydra that provokes physical retaliation. Temporarily, Valkyrie enlarged Akina’s breasts using the Key of Time at Hydra’s suggestion during the second season, granting fleeting satisfaction before the alteration was reversed. Akina is also an exceptionally poor karaoke singer.

When arguments with Hydra intensify, they fuse into a single warrior named Akidra, merging their powers and enabling internal communication; the fusion dissolves upon mutual agreement. Akina discovered this ability while confronting a Valkyrie Ghost. Additional challenges include a cat allergy and Hydra-induced misery during a season-one incident where age regression transformed Akina into a child.