Japanese digital consumer electronics manufacturers are said to have lost in key markets. According to product architecture theory, one cause for the decline is that the technology has been modularized by IT. Similarly, technology is being modularized in the financial industry. FinTech, a cheap and simple financial technology for smartphone applications, is emerging. This innovation is similar to the modularization experienced by Japanese digital consumer electronics manufacturers. As a result, there is a possibility that both Japanese financial institutions and digital home appliance manufacturers will exit key markets. Based on case studies, this work examines a strategy to prevent Japanese financial institutions from declining and collapsing in the same way as digital consumer electronics. Therefore, the strategy is considered from the viewpoint of architecture and business ecosystem theories, not financial or financial institution theories. In addition, this study proposes management strategies that Japanese financial institutions should adopt.