The drive toward sustainable energy and decarbonization has intensified due to growing concerns about climate change. Heat source systems are major energy consumers in buildings, and digital twin technology has emerged as a crucial concept for enhancing efficiency through real-time monitoring and operation optimization. This paper introduces Waseda University's ongoing project, “Development and Standardization of Fundamental Technologies for Thermal Energy Management Systems” (FUTTEMS). The project aims to digitize heat management by integrating various heat utilization devices from different manufacturers. The long-term goal of this project is to develop foundational technology that can optimize the entire energy supply and demand system—including heat, electricity, and hydrogen in the future. The project is organized around three main themes: (1) Carbon-Neutral Campus, which focuses on creating a carbon-neutral environment using Waseda University's campus as a case study. This involves integrating advanced technologies, such as low-GWP turbo chillers, absorption chillers, and innovative liquid desiccant systems for air conditioning and ventilation control through digital twin technology to achieve a 50% reduction in carbon emissions. (2) Sustainable Decarbonized Agriculture and Cold Chains, which aims to reduce greenhouse gas emissions in the agriculture and food supply chain by developing a “Green Value Chain Platform” and implementing energy management systems (EMS). (3) Diversified Utilization of Heat Pumps that seeks to promote the widespread adoption of high-temperature heat pumps through the introduction of EMS and digital twin technology. This initiative is expected to play a key role in achieving carbon neutrality, particularly as renewable energy sources become more prevalent.