Matsuri Shihou is the female main protagonist of the anime sola. She appears as a young girl with long purple hair and purple eyes, and she first meets the series' other central character, Yorito Morimiya, during his early-morning attempts to photograph the sunrise. Matsuri is a Yaka, a supernatural being also known as a Calamity of the Night, and she has lived for hundreds of years. Her body is fundamentally harmed by direct exposure to sunlight, which forces her to be active primarily at night or on overcast, rainy days. Because of this limitation, she has never been able to stand beneath the open sky during the day, and her greatest wish is to one day see a true blue sky, much like the ones captured in photographs.

Matsuri's personality is initially marked by a quiet, somewhat detached demeanor that reflects her long and solitary existence. She is a strange and mysterious figure when Yorito first encounters her, struggling with a vending machine to get a can of tomato juice. As she becomes more comfortable with him, she reveals a more vulnerable and emotionally layered side. She carries the weight of a tragic past shaped by centuries of loneliness and the knowledge that her very nature as a Yaka means she is meant to be alone. Her motivations are deeply tied to her longing for the sky and her desire for genuine connection, which she finds herself slowly building with Yorito through their shared fascination with the heavens.

In the story, Matsuri serves as the supernatural catalyst around which the plot revolves. She is introduced as an enigmatic figure pursued by Takeshi Tsujidou, a man who seeks to kill her. Yorito, after witnessing her powers and learning her true nature, chooses to protect her and invites her to stay at his home. This decision sets the central conflict in motion, as Matsuri must navigate her growing bond with a human while being hunted by those who view her existence as a threat. Her role deepens as the narrative explores the history of the Yaka and her own connections to other characters, including Aono Morimiya and Mayuko Kamikawa.

The key relationship in Matsuri's story is with Yorito Morimiya. Initially, she is cautious and reluctant to form a close attachment, but over time she falls in love with him. Yorito's kindness, his passion for photographing the sky, and his willingness to accept her despite her dangerous nature give her a sense of hope she has not felt in centuries. Their relationship is central to her emotional development, as it challenges the belief that Yaka are doomed to eternal solitude. She also has a complicated history with Aono Morimiya, whom she regards as an enemy, and a more amicable connection with Mayuko Kamikawa, who is identified as a friend. She was formerly an enemy of Takeshi Tsujidou before their dynamic shifted.

Over the course of the series, Matsuri undergoes significant development. She begins as a guarded, world-weary being who has accepted her fate as an isolated creature of the night. Through her interactions with Yorito and the events that force her to confront her past, she gradually opens up and learns to trust. She struggles with fear that her powers will harm those around her and that her past mistakes will catch up to her, but she eventually finds the strength to face her history and seek a measure of peace.

Matsuri possesses several notable abilities as a Yaka. She has enhanced physical strength, a rapid regenerative ability that allows her to heal from wounds, and an ageless body that makes her effectively immortal under normal circumstances. Her most distinctive power is the ability to cause rapid decay in anything she touches. Through direct physical contact, she can make materials such as metal, stone, flesh, and bone rot and deteriorate almost instantly. This ability makes her a formidable force but also a dangerous one, reinforcing her isolation and the fear others have of her. She can be killed only by excessive exposure to sunlight or by receiving fatal wounds that cannot heal in time.