This paper discusses the issue of reconstructing Proto-Japonic demonstratives. Since demonstratives constitute a small and closed set, they are subject to internal pressures from other items within the paradigm. Therefore, a theoretical approach that emphasizes analogy, compounding, and reduction—processes operating within the system—is required.Building on this framework, the paper explains the differences between Old Japanese and Proto-Ryukyuan as resulting from two reductive processes from Proto-Japonic: *sə- ə- ( o-) in Proto-Ryukyuan, and ka- a- in Proto-Northern Ryukyuan.These developments support identifying the Proto-Japonic demonstrative system as comprising kə- and ka- for proximate and distal deictic nouns, respectively, and sə- for anaphoric nouns, with adverbial ka- used to refer to proximate manner.Although the status of the anaphoric pronoun si in Old Japanese remains unclear, further investigation of the Ryukyuan languages may help clarify its relationship to sə- in Proto-Japonic.
Tomohide Kinuhata (2025) studied this question.