Hiro Kinashi, known by the nickname Retro, is a supporting character in the competitive karuta world of the series. He is a tall, slender young man with a pale complexion and a distinct black bowl-cut hairstyle, often seen with his eyes closed. His nickname in the original Japanese, Hyoro, means lanky, which suits his physique. He dislikes his moniker and frequently asks others to call him by his given name, Hiro.

Hiro is a member of the Hokuo Academy Karuta Club, where he eventually becomes president. As a player, he is highly competitive and strategic, known for relying on a specific set of prominent cards he calls his Retrot cards, a term that blends retro with tarot. Fellow player Akihito Sudo notes that Hiro is correct in his judgments about eighty percent of the time. Despite this analytical skill, he struggles to achieve Class A ranking, which becomes a personal challenge, especially after taking on the responsibility of leading his club. In team matches, he often does not hold the captain position but chooses to play against the opposing team's strongest ace players, a tactical sacrifice that gives his own teammates a better chance of winning. He also takes pride in personally recruiting all the freshman players and is dedicated to nurturing those who may not have natural talent.

Within the story, Hiro is initially presented as competition for the Mizusawa Karuta Club, but after his team loses to them, he gains respect for their players, particularly Chihaya Ayase. He has known Chihaya the longest among his peers, though they have rarely faced each other directly in a match, a situation he believes is because Chihaya prefers to seek out stronger opponents. He regards both Taichi Mashima and Arata Wataya as his rivals, considering Arata his eternal rival since a fateful encounter with him during their sixth-grade year. His relationship with Sudo is somewhat ambiguous; while he is on good terms with him, he also finds Sudo's intense pressure uncomfortable and has called him a sadist.

Hiro plays a notable role in team dynamics, often serving as a strategic anchor for Hokuo Academy. His defining ability is his reliance on his Retrot cards, a unique method where he appears to divine his team's fate based on these cards. However, he is not bound by the results they present, as shown when he chose to ignore their reading to prove his team's strength. His development is marked by his transition from a player who depends on his cards to a club president who shoulders the responsibility of building and nurturing his team, showing a deeper commitment to the growth of his club members even while he personally struggles to advance his own ranking.