This chapter explores quantitative aspects of two linguistic variants in Japanese case particles undergoing linguistic change. While there are extensive studies on the phenomena from theoretical perspectives, as well as quantitative studies providing evidence for the changes, previous studies have limited analyses of how such changes proceed through interactions with extralinguistic conditions, due to the lack of diverse situational data with adequate context. With the recent advent of the Corpus of Everyday Japanese Conversation (CEJC) corpus, the chapter addresses this gap by employing the corpus with rich social information. The findings offer new insight into the dynamics of linguistic change, highlighting that the use of the variants varies according to social contexts. Specifically, in the nominative/genitive alternation (NGA), (i) females are leading the change where nominative subjects are the innovative form, and (ii) the preference for nominative subjects in business discussions suggests it might be the prestige form, indicating that the current stage is a case of ‘change from above.’ In the case of the nominative/accusative alternation (NAA) in desiderative adjectives, (i) accusative objects might be the prestige form, and (ii) the gender difference suggests that females might be leading an ongoing change by using nominative objects more frequently than males.