Sony Bank and Fujitsu apply Generative AI to Core Banking System Development

Tokyo and Kawasaki, Japan, September 14, 2026 - (JCN Newswire) - Sony Bank, Inc. (Sony Bank) and Fujitsu Limited (Fujitsu) today announced the full-scale application of generative AI in the development of Sony Bank's core banking system, starting in September 2025. By establishing a mechanism for AI to utilize development assets such as design documents, source code, and test assets, and gradually expanding its application to key processes from design to manufacturing and testing through actual development, the companies have confirmed a 30% reduction in the development period from basic design to integration testing as of July 2026, compared to conventional methods.

The system adopts Fujitsu's core banking solution, "Fujitsu Core Banking xBank"[1] ("Core Banking xBank"). "Core Banking xBank" features a cloud-native architecture operating on Amazon Web Services (AWS), providing an environment that enables rapid integration and trials with generative AI services. This environment allowed for the phased application of generative AI to each process.

In this initiative, an AI agent centered on Anthropic PBC's "Claude"[2] on “Amazon Bedrock”[3] is utilized across processes, with human oversight for final judgment and quality assurance. The use of generative AI is not limited to proof-of-concept (PoC) but has been established as a development process for a core banking system in live operation.

Sony Bank and Fujitsu will leverage the knowledge and development assets gained from this initiative to other processes and systems, further deepening and expanding the use of generative AI at Sony Bank. Fujitsu will also apply the knowledge gained from this initiative to future "Core Banking xBank" development and development for other financial institutions, contributing to the advancement of financial system development.

Background

It can take Japanese financial institutions several months to years to move from planning to launching new services, and high development costs and complex development processes have made it difficult to respond quickly to rapidly changing market environments. As generative AI matures, the ability to embed it into live development processes is becoming a competitive differentiator.

Amidst this, both companies, together with Amazon Web Services Japan (AWS Japan), have been promoting the transformation of the development process for core banking systems, which are the foundation of banking operations.

Overview of the Initiative

Starting in September 2025, Sony Bank and Fujitsu are utilizing Anthropic’s "Claude" model and other models provided on Amazon Bedrock. In this initiative, generative AI transforms the entire development process by leveraging design documents, source code, and test assets across all stages.

This initiative has resulted in a 40% reduction in man-hours and a 30% reduction in development period for processes from basic design to integration testing. Specifically, the companies confirmed up to a 90% reduction in impact assessment man-hours in the basic design phase, up to a 40% reduction in design document creation man-hours in the detailed design phase, a 99% source code generation rate in the implementation phase, and up to a 90% reduction in test execution man-hours in the integration testing phase.

Figure 1: Expansion of Generative AI Applications and Key Benefits (As of July 2026)

1. Transformation to an AI-centric development process

Generative AI is applied not only to specific processes such as coding but across major development processes including basic design, manufacturing/unit testing, and integration testing. Furthermore, an AI agent centered on "Claude" and "Claude Code"[4] on Amazon Bedrock utilizes development assets such as design documents, source code, and test assets of Sony Bank's core banking system across processes. By generating source code and test cases from design documents and reusing deliverables from upstream processes in subsequent processes, inter-process collaboration is strengthened, leading to improved development efficiency. In addition, each AI agent supports development by linking with necessary development assets and various tools[5], under human judgment, approval, and quality assurance, thereby achieving both quality and productivity.

2. Application to to actual development, not just PoC

This initiative applies generative AI to the actual development of a live core banking system, not just to conceptual PoCs or limited trials. It is also utilized in the development of various applications that support banking operations, including online transaction processing and batch processing, demonstrating practical application regardless of processing type. Furthermore, by incorporating generative AI into the standard development process and having Fujitsu personnel with expertise in financial operations and system development evaluate and improve it at appropriate times, the scope of application is expanded while ensuring safety and quality.

3. High compatibility with "Core Banking xBank"

The cloud-native and microservices-based architecture adopted by "Core Banking xBank" serves as a crucial foundation for leveraging generative AI. The environment operating on AWS enables rapid integration and verification with generative AI services, and the microservices structure allows for phased application and evaluation on a function-by-function basis. As a result, generative AI was continuously applied to each of the design, implementation, and testing processes, and its effectiveness was verified, leading to an expansion of its application scope.

Figure 2: Overview of the Initiative

Future Plans

Sony Bank and Fujitsu will proceed with the application of generative AI to the entire development process, including requirements definition, and gradually expand its application to security, operations, and maintenance areas. Furthermore, the knowledge and development assets gained from this initiative will be utilized in peripheral systems, further deepening and expanding the use of generative AI at Sony Bank. Sony Bank aims to become an "AI-native bank" that can quickly respond to changing customer needs and business environments by continuously utilizing AI.

Fujitsu plans to extend this model to other financial institutions adopting "Core Banking xBank," supporting the broader modernization of banking systems in Japan. The knowledge and feedback gained from this initiative will also be utilized in the development of "Uvance for Finance AI Transformation Platform", a dedicated AI platform that supports AI utilization for financial institutions, aiming for further sophistication of AI-driven system development. Additionally, through Uvance for Finance, which enhances financial operations with data and AI, Fujitsu will accelerate system development for financial institutions and advance the continuous transformation of financial services.

Figure 3: Illustration of the Expansion of Generative AI Applications at Sony Bank

Tatsuya Fukushima, Executive Officer, Sony Bank Incorporated comments:

Sony Bank considers the advancement of system development capabilities as one of its critical management challenges to respond quickly to changing customer needs and business environments. The successful full-scale application of generative AI to the development of our production core banking system is a significant step towards becoming a bank that continuously evolves based on AI. We will continue to promote our evolution into an AI-native bank while ensuring safety and quality through collaboration with Fujitsu, AWS Japan, and Anthropic.

Masaru Yagi, Corporate Executive Officer, EVP, Fujitsu Limited comments:

Fujitsu is promoting the provision of "Core Banking xBank" as a mission-critical foundation that supports the transformation of financial institutions. This initiative is an advanced example of the full-scale application of generative AI to the actual development of a core banking system on "Core Banking xBank," demonstrating a new model for financial system development. We will continue to collaborate with Sony Bank, AWS Japan, and Anthropic to further promote the practical application of AI in the Japanese financial industry.

Yasuhiro Kose, Executive Officer, Amazon Web Services Japan comments:

Applying generative AI across design, build, and testing in the live development of a bank's core banking system, and achieving a 30% reduction in development time while maintaining the compliance and reliability the industry demands, is a significant milestone for the Japanese financial services. This is exactly the kind of initiative Amazon Bedrock was built to support.

Hidetoshi Tojo, Executive Officer, Head of Japan, Anthropic Japan G.K. comments:

A banking system carries the trust of every customer, so it is essential that organizations use trusted AI that can be applied safely to work of this consequence. Sony Bank and Fujitsu are doing just that by applying Claude across the design, development, and testing of a production core banking system, with human judgment and quality assurance at every stage. We are proud to work alongside Sony Bank, Fujitsu, and AWS Japan on a model Fujitsu will now carry to other banks in Japan.

[1] “Fujitsu Core Banking xBank”:
A core banking solution with a cloud-native application architecture.
[2] “Claude”:
A family of large language models provided by Anthropic.
[3] “Amazon Bedrock”:
A fully managed generative AI service provided by AWS.
[4] “Claude Code”:
An AI coding tool provided by Anthropic that supports software development. It assists with generating, modifying, and reviewing source code.
[5] various tools:
MCP (Model Context Protocol), Tools, Skills, etc., that enable AI agents to interact with external systems and data to retrieve information and execute business processes.

About Sony Bank, Inc.

Sony Bank was established in 2001 as an online bank with a primary focus on individual customers in Japan. Sony Bank is a subsidiary of Sony Financial Group Inc. Our mission is to bring customers convenient, high-quality financial products and services. https://sonybank.jp/lang=en

About Fujitsu

Fujitsu’s purpose is to make the world more sustainable by building trust in society through innovation. As the digital transformation partner of choice for customers around the globe, our 100,000 employees work to resolve some of the greatest challenges facing humanity. Our range of services and solutions draw on five key technologies: AI, Computing, Networks, Data & Security, and Converging Technologies, which we bring together to deliver sustainability transformation. Fujitsu Limited (TSE:6702) reported consolidated revenues of 3.5 trillion yen (US$23 billion) for the fiscal year ended March 31, 2026 and remains the top digital services company in Japan by market share. Find out more: global.fujitsu

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