Ui Ui is a mature and proper young man who really doesn't display any typical traits for someone his age. He's defined by his loyalty and devotion to his sister. He worships Mei Mei and is more than happy to do all of her biddings, even willing to die for her. Ui Ui expresses great disdain toward any individuals who inconvenience or disrespect Mei Mei in any way. He wasn't very friendly with Yuji while they were on the same team in Shibuya simply because he was too close to Mei Mei.