OpenAI deepens Japan footprint with Hitachi deal
Hitachi will use OpenAI's Codex agent to unpick ageing mission-critical systems and gain early access to its frontier AI models in a slew of high-profile Japanese partnerships for the US AI lab
Japanese industrial giant Hitachi has teamed up with OpenAI to address two of the most pressing technology challenges facing large enterprises: ageing legacy infrastructure and looming cyber threats.
Forward deployed engineer (FDE) teams from the two companies will use OpenAI’s Codex AI agent to analyse the source code of mission-critical legacy systems in a major IT modernisation effort – from reverse-engineering high-level specifications to migration testing for new systems – that will initially target financial institutions before being rolled out across a broader range of industries.
Hitachi president and CEO Toshiaki Tokunaga said modernising legacy systems and bolstering security were “critical management priorities” for enterprises seeking sustainable growth in the AI age, noting that the company currently operates 15,000 systems that support mission-critical social infrastructure in Japan alone.
Hitachi will also gain access to OpenAI’s AI models for defensive cyber security purposes through the Trusted Access for Cyber (TAC) programme, part of OpenAI’s broader Japan Cyber Action Plan. Under OpenAI’s Daybreak initiative, Hitachi’s Cyber Centre of Excellence will use the models internally to identify vulnerabilities, test remediation, and validate systems, with appropriate safeguards, governance, and human oversight.
The expanded partnership builds on a memorandum of understanding signed in October 2025, which focused on applying OpenAI's frontier AI technology to Hitachi’s Lumada data analytics and internet-of-things (IoT) platform.
Insights from both the modernisation and cyber security initiatives will be used to improve HMAX, Hitachi's next-generation AI solution suite for social infrastructure. The company's frontier AI deployment centre will lead the product enhancement efforts.
Tadao Nagasaki, president of OpenAI Japan, noted that the partnership with Hitachi is “an important step toward enabling the safer and more practical use of AI in Japan’s critical industries and social infrastructure”.
“Through this work, we will help create an environment where companies can use AI with confidence and create new value, while helping AI become a practical force that expands the potential of people and organisations and supports the society of the future,” he added.
OpenAI's growing Japanese footprint
The Hitachi deal is the latest move by OpenAI to expand its footprint across Japan’s enterprise and government sectors.
In late 2025, OpenAI launched a joint venture with SoftBank to provide AI offerings based on OpenAI’s latest products, along with implementation and system integration services. Earlier this week, SoftBank also announced an AI-powered patching service using the joint venture’s technology, aimed at the country’s top 3,000 companies that operate critical infrastructure such as transportation, power systems and airports.
On the enterprise IT side, NTT Data became the first Japanese company to distribute OpenAI services, striking a partnership in April 2025 to offer ChatGPT Enterprise to businesses in Japan. NTT Data has set a target of achieving cumulative sales of 100 billion yen ($700m) in OpenAI-related ventures by the end of fiscal year 2027.
OpenAI has also moved to embed itself in Japanese government infrastructure. In October 2025, OpenAI and Japan's Digital Agency announced a partnership under which an AI tool called Gennai, powered by OpenAI’s technology, would be made available to government employees to drive innovative public sector use cases.
In cyber security, OpenAI has been pitching its models directly to Japan’s financial regulators and banks. Japan’s finance minister Satsuki Katayama confirmed last month that some Japanese financial institutions were granted access to OpenAI’s GPT-5.5-Cyber model under the same TAC verified-defender programme to mitigate growing cyber attacks targeted at the financial sector.
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