Dex acts very arrogant and boastful. He cares very much for his little brother Chisao, often panicking when he gets in trouble, and tries to maintain his respect in both the games and the anime. He also has a rivalry with Lan Hikari and the two compete whenever they can, usually by Netbattling. He and Lan are similar in that they forget to do homework and do poorly in class. Dex also gets very mad when Maylu Sakurai hugs Lan, or shows any kind of affection for him at all. Dex cares deeply for his friends and is willing to risk his life for them.
- Dex's Japanese name Dekao includes the Japanese word 'dekai', which means 'huge', while his brother's name Chisao includes 'chiisai', which means 'small'.