Detecting Sensitive Personal Information in Japanese Pre-Training Corpora for Large Language Models

Rei Minamoto, Yusuke Oda, Daisuke Kawahara


Abstract
Sensitive personal information can appear in large-scale pre-training corpora for large language models (LLMs). Detecting and filtering such information is therefore essential to ensure compliance with privacy regulations and prevent unintended information leakage. However, in contrast to English and other languages, research into sensitive personal information has been limited in the Japanese language. In this study, we focus on sensitive personal data defined as special care-required personal information (SCPI) under Japan’s Act on the Protection of Personal Information (APPI). We construct an SCPI dataset using LLM-based annotation and train machine learning models to rapidly detect SCPI in text. As a result, our SCPI classifier can effectively identify information related to SCPI. This study is the first to explore SCPI detection in Japanese text corpora, highlighting the challenges of accurate detection.
Anthology ID:
2026.findings-acl.653
Volume:
Findings of the Association for Computational Linguistics: ACL 2026
Month:
July
Year:
2026
Address:
San Diego, California, United States
Editors:
Maria Liakata, Viviane P. Moreira, Jiajun Zhang, David Jurgens
Venue:
Findings
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Publisher:
Association for Computational Linguistics
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Pages:
13341–13354
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URL:
https://preview.aclanthology.org/ingest-acl/2026.findings-acl.653/
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Cite (ACL):
Rei Minamoto, Yusuke Oda, and Daisuke Kawahara. 2026. Detecting Sensitive Personal Information in Japanese Pre-Training Corpora for Large Language Models. In Findings of the Association for Computational Linguistics: ACL 2026, pages 13341–13354, San Diego, California, United States. Association for Computational Linguistics.
Cite (Informal):
Detecting Sensitive Personal Information in Japanese Pre-Training Corpora for Large Language Models (Minamoto et al., Findings 2026)
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https://preview.aclanthology.org/ingest-acl/2026.findings-acl.653.pdf
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