Angelina Kudou Shields, or "Lina," is a young girl with bright blonde hair styled in twin-tails and sparkling blue eyes. She is a Lieutenant Colonel and the Head-Captain of "STARS," the elite magic unit of the USNA (United States of North America). She is also one of the world's 13 Strategic-Class Magicians under the code name "Angie Sirius," wielding devastating Strategic-Class magic such as Heavy Metal Burst and Brimstone.

As an exchange student at First High School, Lina tries her absolute best to project an image of a flawless, high-achieving, and approachable student to keep her true identity hidden. She presents herself with a polite, bright, and cheerful demeanor, being friendly to everyone in class. She always wears a warm smile and actively tries to participate in normal teenage activities with her peers.

However, beneath this perfect facade, she frequently slips up and loses her composure. Unfamiliar with Japanese culture and a regular high school life, she reveals a clumsy, awkward side and gets deeply flustered whenever she makes a mistake. Furthermore, whenever she feels backed into a corner or caught off guard by Tatsuya, her tsundere nature fully comes out—pouting, raising her voice to hide her embarrassment, or trying to act tough to cover up her panic.