I was deeply saddened and shocked to hear the news of Prof. Yongseok Oh’s passing. Traveling to Daegu to attend his funeral, I was struck by a photo of him smiling, which made me feel his absence even more keenly.

My acquaintance with Yongseok Oh began during my second year of graduate school when I was pursuing a master’s degree. At that time, he was a PhD student at Seoul National University, and we frequently participated together in seminars on theoretical nuclear physics. Our conversations brought me great comfort as I worked on my master’s thesis, trying to replicate the static properties of the nucleon within the Skyrme model. Being new to the field, I lacked guidance, and Yongseok proved to be an invaluable resource. As a theoretical physicist, he possessed extensive knowledge about the Skyrme model in the bound-state approach. In fact, he generously shared his technical notes on the Skyrme model with me.

After completing my master’s degree, I pursued further studies in Germany, leaving behind the academic environment where Yongseok and I had formed our connection. During my time in Germany, I had the opportunity to read his papers on properties of the singly heavy baryons within the Skyrme model in the bound state approach, which earned significant citations in the field of hadronic physics. Later, he began working on hadronic reactions, focusing on the production of various mesons and baryons, which aligned with my interests during my PhD studies. When I returned to Korea, our relationship was rekindled. In 2001, he, alongside Taesoo Song and Su Houng Lee, co-authored a highly important paper on J/ψ absorption by π and ρ mesons with anomalous parity interactions, which left a profound impact on the hadronic physics community.

In 2011, my PhD student Sang-Ho Kim and I collaborated with him to understand K^* Lambda photoproduction, considering higher nucleon resonances. This collaborative effort was crucial in comprehending experimental data from the CLAS Collaboration at Jefferson Laboratory. Working together, I thoroughly enjoyed discussing the physics of hadronic productions with him.

Beyond his impressive research contributions, Yongseok took on responsibilities as a coordinator for APCTP, and I was impressed by his organizational and management skills. As a member of the Division of Nuclear Physics in the Korean Physical Society, I witnessed him organizing various workshops and conferences. He was also actively involved in the activities of nuclear physics in the AAPPS Bulletin. Recently, he put great effort into an upcoming project related to the Electron–Ion Collider, which will be constructed in the USA. Unfortunately, I believe his tireless efforts took a toll on his health. In March 2023, during a J-PARC workshop held in Tokai, Japan, I had the opportunity to have lunch with him, and we discussed physics and the future of the nuclear physics community in Korea. Little did I know that it would be our final meeting. Three weeks later, one of my postdocs, a former student of the late Prof. Yongseok Oh, came to my office and conveyed the sad and shocking news of his passing. I still cannot fully express my feelings and sorrow upon hearing this news. I extend my heartfelt condolences to his wife and family.