ABSTRACT First Person is a series of interviews with the first authors of a selection of papers published in Journal of Cell Science, helping researchers promote themselves alongside their papers. Kazutoshi Takebayashi is first author on ‘ Field model for multistate lateral diffusion of various transmembrane proteins observed in living Dictyostelium cells’, published in JCS. Kazutoshi is a research associate in the lab of Masahiro Ueda at the BioSystems Building, Osaka University, Japan, focusing on diffusion analysis and modelling of transmembrane proteins in living cell membranes.