Even shortly after he was born, Kageyama was shown to already have a great love for volleyball when he held on dearly to his older sister's volleyball and refused to let his grandfather take it away from him[2]. When he was around four years old, Kageyama started playing volleyball with his grandfather, Kazuyo, and his older sister, Miwa, and soon found a passion for the sport, and became a setter due to it being the position that got to touch the ball the most. During his time at Akiyama Elementary, Kageyama is soon recognized as a prodigy.
Once he entered Kitagawa Daiichi Junior High, it was clear that his potential would be much higher than the other players on his team, including the current third-year setter Tōru Oikawa. However, Kageyama's exceptional abilities and lack of consideration for others led him to develop a demanding demeanor and an inability to cooperate with his teammates, causing them to refer to him as the "King of the Court". Since the true meaning of this nickname was only known to the players at Kitagawa Daiichi, outsiders simply assumed that it referred to Kageyama's incredible talent. Additionally, he would often practice more than required, which his teammates, Kunimi and Kindaichi, would notice and judge him for and at times try to avoid.
By his third year of junior high, Kageyama's attitude had already destroyed his relationship with his teammates to the point where Kindaichi and Kunimi considered asking the coach to bench the setter. Despite the setter's lack of teamwork, Kitagawa Daiichi still managed to be a favorite to win at the Junior High Athletics Meet. It was at the tournament where he would first meet and begin his long-term rivalry with Shōyō Hinata.
Kitagawa Daiichi was said to have moved forward with the tournament but lost in the finals; it's hinted that Kageyama may be one of the main reasons for the loss due to his picture being on an article about the match. At some point during the junior high competitions in his third year, Kageyama sent a toss to his teammates in the middle of a game only to find no one behind him. His teammates refused to hit his tosses anymore, showing their clear desire of having him removed from the team. Kageyama was then benched and ended his final game at Kitagawa Daiichi in shame. Not long after this, Kageyama fails to enter Shiratorizawa and his grandfather passes away, which is shown deeply affecting him and his sister, Miwa.
Kageyama's height and impressively sharp glare are said to be his most prominent physical features and source of attraction to several female classmates. He is of a lean but muscular build. He often emits an intimidating aura, which is heightened by the almost permanent scowl on his face. His black hair is cropped short, with a fringe that hangs just above his dark blue eyes. His typical attire consists of either his school uniform or practice clothes.
Post-timeskip, Kageyama has grown to be 188 cm. His hair is now parted down the middle similar to that of how Kunimi had his. By the end of the series, Kageyama now has short bangs that end just above his eyebrows.