Karla Amatsu is a character from the anime The Vexations of a Shut-In Vampire Princess. She is a fifteen-year-old girl belonging to the Wakonsu race, a Japanese spirit lineage, and she always appears dressed in a traditional kimono, which complements her long, straight black hair. Her beauty is frequently noted, with those around her going so far as to call her a once-in-a-trillion-years beauty, though she herself pays little attention to such praise.

In public, Karla is known as one of the Five Sword Emperors, a title given to the most powerful generals of the Amaterasu Nirvana Army, where she serves as the leader of the Fifth Unit. She is also a member of the group known as the Six War Princesses. Following the events of the Tenbu Festival, she accepts the role of the High Deity of Amaterasu. Despite these grand and powerful titles, Karla’s actual combat ability is virtually nonexistent. She obtained her positions of authority solely through her influential family's connections, as she personally has no talent for or interest in fighting. In fact, she is terrified of battle, conflicts, insects, and notably, her own grandmother.

The stark contrast between her fearsome reputation and her true nature is central to her personality. While she presents a calm, level-headed, and dignified exterior befitting a general, Karla is privately a lazy and easygoing young woman. Her greatest passions are napping and creating traditional Japanese confections, known as wagashi. Her true dream is not to rule a nation but to become the finest wagashi artisan in the capital. To that end, she secretly runs a sweets shop called Fuzentei, located on the outskirts of the capital. Her skills extend far beyond the kitchen; she is remarkably proficient in almost every other field, including cooking, cleaning, sewing, calligraphy, ikebana, poetry, koto music, financial management, corporate governance, and even national administration.

Her most notable ability is her special power, a type of Retsukaku Liberation known as Raging Tamayura. This power allows her to reverse the flow of time for a chosen target by consuming her own willpower. The ability is considered incredibly powerful, but it carries a significant risk. If Karla uses it too much, her very existence is endangered, and she could disappear completely. Because of the danger, her power was initially sealed away using a divine artifact crafted by a character named Rone Cornelius.

Karla’s role in the story begins when she arrives in the Mulnite Empire as an emissary to seek an alliance. Her initial encounter with the protagonist, Terakomari Gandesblood, is comical, as Karla mistakenly believes the timid vampire princess is a fearsome murderer. However, after they participate in the Tenbu Festival together and come to understand each other, they quickly become close friends. Karla values this friendship greatly and often provides a reliable, if occasionally lazy, ally for Komari. Throughout the series, she shows deep care and concern for her cousin, Kakumei Amatsu, who has run away from home, and later displays a protective jealousy regarding his romantic life.

Over the course of the narrative, Karla experiences significant character development. She begins as a general unwillingly forced into the role due to family pressure, simply wanting to run her sweets shop. However, after the events of the Tenbu Festival, she changes her perspective and accepts her responsibility, becoming the High Deity of Amaterasu. Even after ascending to this divine leadership role, she never loses sight of her simple dreams. She continues to see herself first and foremost as a confectioner and remains dedicated to running her shop, Fuzentei, using her high office not for conquest but to gently protect her country and the people she cares about.