My Life as Inukai-san's Dog.

犬になったら好きな人に拾われた.

After eating chocolate handed to him by the eccentric Inari Sakahira, an unnamed high school student wakes up transformed into an Akita Inu puppy. He is picked up by Karen Inukai — the cool, unreadable classmate he has a crush on — who showers her new pet with open affection she never shows at school. Trapped in a dog's body with his memories and feelings intact, he navigates life as Karen's pampered and increasingly conflicted household dog.