Setsuna Kai is a character from the Devil Children series. He is the protagonist of Devil Children Black Book and his partner is the Cool the Cerberus. He's known as Serina in DemiKids. (source)

Default outfit: blue jacket, purple jacket, long sleeves, high collar, black turtleneck, black gloves, partially fingerless gloves, blue shorts, purple shorts, black belt, bike shorts under shorts, white socks, sneakers

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