Karen Inukai is the main heroine of the story and a high school student who initially appears to be a cool, expressionless, and aloof girl. She has a striking appearance, characterized by hip-length black hair, often styled in a braid at the back, paired with a white headband and red eyes. Her public demeanor is one of emotional reserve; she acts curt and distant not only with her classmates but also with her own mother, which often leads to misunderstandings and her feeling isolated at school. However, this cold exterior is a carefully constructed act, a defense mechanism born from a painful childhood trauma. As a child, Karen deeply loved a dog named Pochita, and when it died, she shut down emotionally to protect herself from that kind of grief. The name she gave that original dog carries significant weight, as her surname, "Inukai," combines the characters for "dog" and "domesticate," while her given name, "Karen," intertwines "love" and "increase," reflecting her core struggle to express affection.

Behind her facade, Karen is an out-of-this-world dog lover. She harbors a deep, warm, and playful affection for canines, which she cannot express toward humans. Her true personality emerges only in private with dogs, where she sheds her detached mask to become cheerful, expressive, and incredibly doting. When she finds a collapsed Akita Inu puppy on the street—coincidentally the protagonist of the story, whom she also names Pochita—she takes him in and pours her passion into caring for him. She nurtures him with meticulous attention, bathing him, documenting his routines, and craving physical closeness, or "skinship," even going so far as to playfully cosplay as a dog to strengthen their bond. She is also notably possessive and jealous when it comes to Pochita, disliking it when he pays attention to anyone else.

Her role in the story is central, with her hidden emotions and her evolving relationship with the new Pochita driving the narrative. The protagonist, who has a crush on her in his human form, gets to experience her secret, tender side as her pet. Karen’s primary motivation is the desire for genuine connection, which she initially only feels is possible with a dog that cannot betray her. Her love for Pochita, who is actually a human boy trapped in a dog's body, becomes the catalyst for her personal development. Through their unconventional bond, she finds a safe space to practice expressing emotion and affection. Her journey shows a slow but steady mending of her past wounds. Encouraged by Pochita's presence at the school cultural festival, she begins to take tentative social strides, interacting with her peers and slowly reintegrating into human relationships. While she gradually learns to open up, her core traits of quiet reserve, a love for dogs, and a mischievous side that takes pleasure in doting on her pet remain steadfast throughout her character arc. Her notable abilities are not supernatural but rather her tremendous capacity for care and her deep, intuitive understanding of dogs, which allows her to form an incredibly powerful and healing bond with them.