Keiji Tanaka, a beloved scientist and a pioneering leader in the field of intracellular protein degradation, passed away unexpectedly from ischemic heart disease on July 23, 2024 at the age of 75. His unparalleled dedication to proteasome research has left an indelible legacy; without his contributions, the field would scarcely be where it is today. His untimely departure marks a profound loss to life sciences and will be deeply mourned by colleagues and researchers worldwide.