Japan’s biggest banks are getting an AI-powered security upgrade, courtesy of OpenAI. The company’s GPT-5.5-Cyber model will be supplied to the Japanese government and select companies starting in May 2026, following negotiations during US Treasury Secretary Scott Bessent’s recent visit to Tokyo.
The three megabanks set to benefit, MUFG Bank, Sumitomo Mitsui Banking Corp. (SMBC), and Mizuho Bank, collectively form the backbone of Japan’s financial system.
The deal behind the deployment
The OpenAI arrangement emerged from broader US-Japan discussions that covered cybersecurity improvements across 15 critical infrastructure sectors.
OpenAI’s contribution comes in the form of GPT-5.5-Cyber, a model specifically designed to bolster defensive security capabilities. The model targets government agencies and a curated list of private sector partners, with Japan’s megabanks sitting near the top of that list.
