Chiaki is supposedly Ran's best friend, his father is a duke and he lives in a really really big house. he's 17yrs old and his height is 5 foot 8 1/2". according to the Author "it's too bad i couldn't have him appear more often. He's sort of a sad individual"
He tries to marry Riko because as a younger child he always came 2nd compared to Ran and he wanted to take revenge so he kidnapped Riko (in his own house -_-) and using inscense to weaken her muscles tried to get him to marry her. But then Ran saves her.