Aki Adagaki is the wealthy heiress to the Adagaki family and a student known as the most beautiful and academically gifted at her academy. She is also athletic and skilled in sports. Her striking appearance features long, dark hair typically styled in two messy low pigtails, fair skin, and a slim figure. Despite her refined image, she has a famously large appetite, which she keeps secret to avoid embarrassment, partly due to a medical condition called hypoglycemia. This habit forces her to eat in private, such as hiding away in a storage room for her large lunches.

Aki has earned the nickname the Brutal Princess or the Cruel Princess for her cruel and dismissive behavior toward boys. She takes pleasure in rejecting their confessions in humiliating ways, often investigating their personal lives to find flaws and giving them insulting nicknames in public. This harsh exterior is a defense mechanism developed from past emotional pain, rooted in the trauma of her parents’ divorce and the sudden disappearance of a childhood friend she had grown to trust, which left her feeling deeply betrayed. She coped with the loss by overeating and built a defensive wall around her heart. It is later revealed that the traumatic rejection she remembers was orchestrated by her maid, Yoshino Koiwai, who impersonated her.

Despite her cruel reputation, Aki is surprisingly naive and lacks common sense about the outside world, having been raised in a sheltered environment. She relies heavily on her personal maid, Yoshino, for guidance in daily tasks and social situations. The relationship is complex, as Yoshino secretly resents Aki and initially aids the protagonist’s revenge plot, but ultimately wants what is best for her and plays a crucial role in reuniting her with her childhood friend.

Aki is the primary love interest and the target of Masamune Makabe’s elaborate revenge scheme, which involves making her fall in love with him only to reject her cruelly. They were close childhood companions until a misunderstanding led to a painful separation, with Aki giving Masamune the cruel nickname Piggy. Initially, she does not recognize the handsome, fit transfer student as the chubby boy from her past, but she finds herself reluctantly drawn to him as he breaks through her defenses. After the eight‑year‑old misunderstanding is cleared up, they reconcile and begin a genuine romantic relationship. Aki has a peculiar preference for his former, chubbier appearance and later makes attempts to fatten him up again. She also has a brief but significant connection to Kanetsugu Gasou, a girl disguised as a boy whom Aki mistakenly accepts as her childhood Masamune due to her desperate desire to reconnect with her past.

Aki undergoes notable development, beginning as a seemingly one‑dimensional cruel princess but gradually revealing her vulnerable, lonely, and caring interior. She confronts her past trauma, learns to trust again, and matures into someone willing to make sacrifices for those she loves. Upon learning the full extent of Yoshino’s deception and her feelings for Masamune, Aki demonstrates profound growth by cutting her long hair short as a symbol of moving on. Ultimately, after Masamune chooses her, she agrees to date him again.