Sustainability science emerged as a new academic field to address complex sustainability challenges. To train sustainability experts, sustainability science programs and sustainability-focused courses are offered in higher education, especially at the graduate level. Given the diverse topics and the complex structures of sustainability challenges, what are the required knowledge and skills needed for sustainability experts? Although the earlier literature identified key features and competencies, empirical studies on how educational programs in sustainability science provide the necessary training are still scarce. This study addresses this gap by illustrating how a field-based course can contribute in developing core skills for fostering sustainability experts through a case study of field-based course called Global Field Exercise (GFE) in the Graduate Program in Sustainability Science-Global Leadership Initiative (GPSS-GLI) at The University of Tokyo. Literature review on the competencies in sustainability science suggests a three-way typology of descriptive-analytical skills, solution-oriented skills, and attitudinal skills. A group of students joined a GFE unit in Akita, Japan, and set “local food and place attachment” as the topic for their fieldwork. The participants conducted semi-structured interviews to three generational groups to illustrate the different perceptions of local food and places. The alternative mechanism of knowledge transmission across generations by local festivals and school events was found. The authors observed the implemented field-based course provided unique learning opportunities to acquire: (i) the ability to perform key competencies collectively instead of individually; (ii) an interdisciplinary-mindset to acknowledge multiple views to topics during group discussions among researchers; (iii) a transdisciplinary-mindset to communicate research outputs with local residents in a communicable way; (iv) the ability to be empathetic to people’s experiences when addressing normative dimensions of sustainability. Although different sets of competencies and approaches for fostering sustainability experts have been studied widely, the field-based approach plays an important role in developing transdisciplinary, interpersonal, and normative competences.