This study explores the complex historical linguistic contact among Japanese, Old Chinese, and Tibeto-Burman languages by comparing related words among the three. First, it was confirmed that Japanese kun-yomi has a regular correspondence with the Old Chinese final stops *-p, *-t, *-k, *-s, *-r, and nasal initials. In particular, the analysis focused on how Japanese kun-yomi retains these phonological features and how both kun-yomi and on-yomi reflect the historical phonological changes of Chinese. Additionally, it was shown that some Japanese words may not be directly borrowed from Old Chinese but instead may have been mediated through Tibeto-Burman languages. This highlights the possibility that Japanese words were not simply borrowed directly from Old Chinese, but other borrowing pathways may have been involved. Through the analysis of allofamic phenomena in phonological changes, the possibility of direct contact between Japanese and Tibeto-Burman languages is also proposed. This study provides new perspectives and insights for the study of historical linguistics concerning Japanese and Trans-Himalayan languages, and offers important directions for future research.