[No. 221] Yudai Nagai

Thank you very much for this opportunity to contribute to the Keio University alumni newsletter. I was born and raised in a Zen temple in Tottori Prefecture. After graduating from the Department of Physics, Faculty of Science and Technology, Keio University, I began my training as a Soto Zen monk and am currently training at a Buddhist temple in the United States. My career path is a bit unusual, but I hope you will enjoy reading this as a story about one of many different kinds of people.

Since I was a child, I have had a vague interest in the natural sciences, and I was particularly drawn to profound questions such as the origins of the universe and life. When I began studying physics in high school, I was completely fascinated by the fact that various natural phenomena are governed by simple, universal laws. Wanting to study physics in earnest at university, I entered the Faculty of Science and Technology, Keio University, and without hesitation, I chose to major in the Department of Physics.

Until my second year of university, classes were mainly lecture-based, allowing me to thoroughly learn the fundamentals of modern physics. In my third year, I remember being busy every week with experiments and reports. During the summer break, I participated in a research camp called the Summer Challenge, hosted by the High Energy Accelerator Research Organization (KEK). Along with students from all over the country and leading researchers, I engaged in full-scale exercises and research presentations on particle and nuclear physics, and also had the opportunity to visit facilities such as the KEK Tsukuba Campus and the Japan Proton Accelerator Research Complex (J-PARC) at the Tokai Campus.

As for extracurricular activities, I was a member of the Yagami Festival Executive Committee from my first to third year. The Yagami Festival is a school festival held every autumn at the Faculty of Science and Technology's Yagami Campus, featuring unique events for the faculty, such as laboratory exhibitions and science classes. I have fond memories of running around the Yagami Campus exhausted, from setting up tents and venues to managing the two-day event and cleaning up all night.

In my fourth year, I joined Professor Yasuhiro Nishimura's laboratory. The Nishimura Lab is involved in international collaborative research using the giant detector "Super-Kamiokande" located in Hida, Gifu Prefecture. Through the observation of neutrinos, a type of elementary particle, the lab works to elucidate the fundamental laws of the universe and its origins. For example, research is conducted to explore the history of the universe's birth and evolution by observing neutrinos released from supernova explosions, and to understand the laws governing elementary particles by attempting to observe neutrinos emitted from the J-PARC accelerator and proton decay. For my graduation research, I focused on the need to improve the identification method for muons and anti-muons to solve the neutrino mass hierarchy problem, and I attempted to measure the lifetimes of both particles in water. At that time, the Nishimura Lab was in its first year, so we started by bringing various equipment into an empty classroom. We designed and assembled the detection device, repeatedly programmed and made adjustments, and somehow managed to advance the research with Professor Nishimura's guidance. I am still very honored to have been involved in the launch of the Nishimura Lab as one of its first members.

Although I was completely immersed in the world of physics, I have been walking a different path since graduating from university.

One day during my third year of university, while visiting my family's Zen temple, I had the opportunity to attend funerals and memorial services. Witnessing the death of a person and interacting with the bereaved families, I became acutely aware of the existence and profound impact of questions and suffering that science cannot answer, such as human life and death. I gradually began to want to explore, in my own way, how to face suffering that cannot be explained from the perspectives of universality, logic, and objectivity. After graduating from university, I spent about two years training as a monk at two training halls: Daihonzan Eiheiji Temple of the Soto school in Fukui Prefecture, and Toshoji Temple in Okayama Prefecture. From 2022, I enrolled in the master's program at Komazawa University's Graduate School of Buddhist Studies, where I researched topics such as the differences in how Zen Buddhism is received in Japan and Western societies.

After completing my master's degree at Komazawa University, I received support from the Yokohama Zenkoji Study Abroad Scholarship for Monks and, as the 37th scholarship recipient, I am currently staying at a temple in the United States called Tassajara Zen Mountain Center (Zenshinji). Zenshinji, founded in 1967 by a Japanese Soto Zen monk, was the first Zen monastery in America. It is located in the mountains of Carmel Valley, California, a five-hour drive south of downtown San Francisco. Although it is a remote area with no cell phone reception, people from all over the world visit to experience Zen training. I am often surprised by the differences in views on Buddhism and monastic training between Japan and the United States, and I am having a very stimulating time.

Of course, the specialized knowledge I gained in the Faculty of Science and Technology is not directly applied in my life as a monk. However, there have been insights gained precisely because I made the leap from physics to the different field of Buddhism. For example, while scientific truth and religious truth often contradict each other, they each support people and society in different domains. I feel that science and religion possess truths of different dimensions. And this may not only apply to the relationship between science and religion but also to the various fields that make up society, such as politics, economics, and medicine. I want to continue my learning as a monk, cherishing a humble attitude that acknowledges the effectiveness and limitations of each field, and sometimes having the courage to approach them asymptotically.