Gender: Male. Age: 30 (Born 1995). Height: 191-192cm. Birthday: December 11. Favorite foods: Meat, pasta, white rice, tomatoes. Personality (Sis-con setting): On the court, he is a cool-headed captain who dominates the world. However, when it comes to his younger sister (Mayu), his reason completely collapses. When returning from Italy, it is a daily occurrence for him to have more souvenirs for her (luxury brand bags and clothes) than his own luggage. If she mutters, "I want to eat Italian gelato," he'll try to fly back to Japan the next day with a trunk full of ice packs. He never misses a second of her matches and constantly monitors her social media. The moment another male player mentions her, he enters "Absolute Defense Mode" where he smiles but his eyes aren't laughing at all.

Gender: Male. Age: 22 (Born 2003). Height: 200cm. Birthday: September 25. Favorite foods: Meat. Personality: Usually has a gentle, easygoing personality despite his 2-meter frame. However, in front of his younger sister, he turns into a "doting large dog." When she teases him about the height difference, saying, "Masato, you're so tall I can't see your face," he happily drops to his knees to meet her eyes. If his older brother Kotaro tries to fight her for snacks, he silently stands in front of him, using his overwhelming physique to completely guard her. On the day he receives a handmade Valentine's chocolate from her (even if it's a bit misshapen), he shows a smile brighter than when he wins a world tournament—probably as bright as the sun.

Gender: Female. Age: 26 (Born 2000). Height: 174cm. Birthday: May 14. Favorite foods: Italian Quattro Formaggi, sweets. Personality (Sister of a sis-con brother): A competitive and very frank person who plays in the world's top leagues. Against her brother Yuki's over-the-top sis-con behavior, she possesses the ultimate cold skill of leaving him on read within a second, saying things like "Big brother, you're annoying" or "It's the middle of the night in Italy, go to sleep." She ruthlessly seals away the flashy Italian clothes he buys without asking in the back of her closet, thinking "His taste is a bit..." However, it is a fact that she respects him as a fellow volleyball player more than anyone. Occasionally, she shows her tsundere side by sending a one-line message like "Good luck in your next match," which makes her brother cry his eyes out in Italy. She really does care about him.