Tonari ni Kanojo no Iru Shiawase: Winter Guest

One autumn day, the protagonist offended his homeroom teacher and thus was ordered to volunteer at the student council. That's where he met the student council leader Shiho, who is completely like an older sister. He wanted to be if only a bit closer to her, but ended up as the student council's dog instead. He spends his days graced by her wonderful smile, while sometimes being swamped with random tasks and sometimes treated affectionately and given snacks. "For me, you'll work like a dog, right?"