Yuu Ishigami

The hidden protagonist of the story. A boy in High School Year 1, Class B → Year 2, Class A. Student Council Treasurer. Born on March 3rd. Blood type O.

He is the second son of a small toy manufacturer and handles the company's accounting. Influenced by his mother, he has a fondness for flowers and is knowledgeable about flower meanings. He always has a lethargic expression and his hair is long enough to cover his eyes. He wears headphones around his neck. His personal pronoun is "I."

In the early part of the main storyline, he (despite having perfect attendance for Student Council activities) only shows up for meetings and usually does his work at home. He was admitted to Shuchiin Academy by his father, who struggled after graduating high school and wanted to show off, but an incident caused him to become truant. However, he was brought out by Shirogane and was soon scouted for the Student Council after entering high school. He significantly contributes to the Student Council through data processing, and Shirogane believes that "the Student Council would fall apart without Ishigami." He loves games, and while he has good innate intelligence, he lacks the motivation to study, leading to many failing grades and being near the bottom of the class. However, with Kaguya's support, his ranking has gradually been improving. In the early part of the series, because Kaguya once harshly rejected his thoughts about her relationship with Shirogane, he tries not to think about it.

Due to a violent incident he caused in middle school, many students look at him with contempt, but he is grateful to Shirogane who saw through the truth of the incident and reached out to him. They have since become very close, even hanging out together on holidays.

He has a high level of human observation, often noticing unnecessary things and stepping on people's landmines. He was especially fearful of Kaguya due to repeatedly witnessing her dark side. However, Kaguya feels close to him, tries to guide him correctly as an important junior, and despite being forceful, helps him out when he's in trouble, leading him to recognize her as surprisingly kind. He harbors an unusual amount of hatred toward athletic students and couples. He has biased knowledge from romantic comedies and often makes inappropriate comments. While with Shirogane, he becomes talkative and sharp-tongued but often ends up emotionally hurt from backlash. Through relentless retorts, he eventually gains the upper hand over Chika, and Shirogane acknowledges him as "the only one who can stand up to Fujiwara (Chika)." He has a poor relationship with Miko of the same grade, but he anonymously sent her encouragement messages and flowers in middle school, and during the Student Council election speech, he asked Shirogane and others to win without mocking Miko because "it irritates me when hard-working people are laughed at." However, he is unaware that Miko's dislike for him stems from him helping her while condescendingly monitoring their truancy issues and school rule violations.

During the sports festival, he developed feelings for Tsubame Koyasu after becoming an executive committee member. At the cultural festival, he unknowingly performed actions considered confessions between students and explicitly confessed to her after the Christmas party. After winter break, motivated by Shirogane’s experiences, he aimed to become the kind of man Tsubame would want to confess to. He confessed again at her graduation ceremony but was rejected and heartbroken.

From elementary to middle school, he was in the soccer club, but he never enjoyed it and quit due to obligation, with average or below-average physical strength. Later, he sought to engage in muscle training.