As young children’s screen time has significantly increased in recent years, their healthy use of digital media is a topic of interest. To support children’s healthy screen use, we are developing Romi, a physical screen peripheral device interface. Romi was designed to help children to transition from screen to out-of-screen by reducing negative experiences when ending screen time. To specify the design concept, we conducted the preliminary interview and experience prototyping focusing on screen-time transition. Based on design attributes which are the peripheral presence, the connection between screen and device, and friendly character, we implemented Romi interface. We believe our approach will provide motivation and inspiration for designing a physical interface for supporting children’s self-regulation.