Deontic Drift in Japanese Translations of the Chinese Civil Code: A Human–LLM Comparison of Deontic Marker Distributions

Deontic expressions determine whether a legal provision imposes an obligation, grants permission, or states a prohibition, making their translation especially important in legal texts. This study compares overt deontic markers in three published human translations and three large language model (LLM) translations of the Chinese Civil Code into Japanese. At the aggregate level, the six translations show similar proportions of obligation, permission, and prohibition. Their total marker counts, however, vary across versions under the same aligned-segment exposure, revealing differences that normalized proportions alone cannot capture. To quantify this variation, we introduce Skew, a descriptive measure that summarizes the overall magnitude of marker-rate drift. In this descriptive comparison, the three published human translations show relatively similar drift profiles, whereas the LLM translations vary more widely and exhibit different patterns. Clause-level examples further show how the observed drift appears through marker retention, omission, and reformulation. These findings demonstrate the value of marker-based analysis for identifying version-level differences in overt deontic-marker realization that remain concealed in aggregate distributions.