Yamauchi Youdou is a character from Lost Property Control Organization (Samidare), a series created by Samidare (Hoshi). He is a student at the school the Protagonist (Lost Property Control Organization) attends, where he is her senior, and appears to have been something of a Delinquent prior to their interactions.
He has short, Red Hair, Red Eyes, and wears his uniform with the shirt unbuttoned