Sagi and Kalas, the main characters of Baten Kaitos Origins and Baten Kaitos: Eternal Wings and the Lost Ocean respectively (left to right).
The flower-petal-looking things represent a Guardian Spirit, which you as the player play as; in Baten Kaitos, you don't technically directly control any character, rather the main characters are known in-universe as Spiriters. It's weird to explain and nobody cares so I'll just shut up now :x