Osamu Saitou originates from the game *Mahjong Soul*, debuting as an unlockable character on the Bamboo Path in the 2020 New Year's First Visit update. He serves as a company director renowned for his calm demeanor, decisive nature, and exceptionally precise, almost robotic daily efficiency. His strict standards apply equally to himself and his employees, earning him the nickname "Devil Boss." His sole noted personal vulnerability is his affection for his high-school-aged younger sister, Mami Saitou. Saitou appears in the 2022 chibi-style anime *Mahjong Soul Pon☆*, featuring comedic everyday stories and mahjong matches with game characters. He returns in the sequel anime *Mahjong Soul Kan!!* (2024), exploring new scenarios beyond the original setting. His visual design includes multiple unlockable outfits: a default look, a "Full Bond" variant, a "Firework Date" costume, and a "Winter Warmth" outfit released during the 2023 Winter Festival. Dialogue excerpts reflect his personality, emphasizing punctuality ("You are 5 minutes 28 seconds late today. For the sake of our cooperation, please be punctual if you can") and reluctantly participating in leisure ("Instead of watching fireworks, I’d rather spend my time reading more reports, or even playing Mahjong for a bit, but… it seems I’m unable to refuse your invitation").