In this paper, we presented two findings: early production of Japanese passive and early mastery of long passives. Together with Sauerland and Alexiadou (2020), we assume the concept PASS to underline passive clauses and be overtly realized in languages that have dedicated passive morphology on their disposal. The central proposal of our paper is the Overt passive morphology hypothesis, according to which the overt special passive morphology facilitates the early acquisition of passive. In this, we build on the 1:1 mapping principle from conceptual representations (CRs) to morphology, developed in Guasti, Alexiadou, and Sauerland (2023). Our analysis is advantageous as it accounts both for languages in which early passive production has been reported and those were passives are delayed.