In the last decade, a citizen participatory culture, advocating citizen participation in public matters as a radical form of direct democracy and demanding its implementation outside the traditional territory of institutional politics, has evolved and expanded dramatically (Krivy and Kaminer 2013). This issue has affected the practice and theory of social innovation and urban planning. South Korea has been recently recognized as a flagship country of this "everyoneism" paradigm in urban design. Following the policies of the current president of the Republic of Korea, Moon Jae-in (2017 ~ present), and Seoul mayor, Park Won-soon (2011 ~ present), many South Korean government agencies are involved in planning citywide social innovation strategies and support social innovation activities in Seoul and other cities by developing participatory methods (tools and programs) that enable citizens to better engage with public spaces or activities in design processes. This research examines these practices and discourses of the citizen participatory turn within the field of urban planning and design in South Korea, particularly in Seoul. From the point of departure in Actor-networking theory(Callon and Latour 1981; Latour 1987; Law 1994), this research critically examines the emergence of citizen as new design practitioners, and questions the role and form of citizen design participation by arguing that their activity should be understood not as an isolated practice, but as a heterogeneous network configuration involving a wide range of actors. Using ethnographic evidence from the particular case of the Seoul Design Governance program structured according to the four moments of a sociology of translation - problematization, interessement, enrolement, mobilization (Callon 1986), paper explores the layers of mediation considering not only the role of citizen designers but also the role of other human and non-human actors, such as policymakers, government structures, professional designers, design tools, guidelines, etc. influ