Elder Sister-Like One, The vol. 1 (manga)

Yuu has had a rough life. After losing his parents in a car accident when he was five, he found himself bounced back and forth among relatives, with no place to truly call home. Plagued by a constant feeling of loneliness, all he wants is a little companionship, and he’s about to get way more than he bargained for! Her name is Chiyo, and she’ll grant Yuu one wish. The only problem: She’s a demon of unimaginable power!