Populism has become a global political phenomenon, spreading across continents. Despite growing scholarship on populist movements, how populist demands are articulated within different political and institutional contexts remains understudied. This paper employs a functional and comparative analysis to examine contemporary European and Japanese populisms, using the European experience as an ideal-type countercase to show how populist pressures (demand-side) are amplified, fragmented, or absorbed within political institutions (supply-side). European and Japanese populism are comparable in key respects: both are wealthy societies with weak economic growth, aging populations, rising migratory flows, and growing distrust toward mainstream actors, with fringe parties blaming institutions for social and economic challenges. In many European countries, populist movements act as polarizing forces, seeking electoral gains and challenging mainstream parties. In Japan, by contrast, populism is more fragmented and largely absorbed by the dominant party system: demands expressed by the Japan Innovation Party and, more recently, Sanseito, are integrated into the hegemonic Liberal Democratic Party. Even when populist demands are similar, political-institutional settings determine divergent outcomes, highlighting the decisive role of institutions. Drawing on party platforms, legislative behavior, and policy outcomes, the paper traces how populist demands are channeled, contained, or amplified.