Mitei Hattori made his debut in 2021 with breakout hit Smile!, which was serialised in Weekly Manga Goraku (Nihon Bungeisha). The series quickly gained attention for its dark psychological themes and bold visual style, establishing Hattori as a striking new voice in the seinen manga scene. Driven by his deep discomfort with forced smiles and inspired by his conversations with people raised in religious cults, Hattori explores themes of faith, control, and the societal pressure to appear happy.