On October 8, 2018, Takagi made his surprise debut in NJPW as the foreshadowed sixth member of the "Los Ingobernables de Japon" stable. Originally performing in the Junior Heavyweight division, he went on to be undefeated as a singles competitor and overall unpinned and unsubmitted until June 2019, winning the IWGP Junior Heavyweight Tag Team Championship once with fellow "Ingobernable" Bushi. He moved to the Heavyweight division later that month. From February to August 2020, Takagi held both the NEVER Openweight Championship and the NEVER Openweight 6-Man Tag Team Championship (with Bushi and Evil), making him the first person to hold both NEVER titles at the same time. After losing the Never Title in August, he regained it in November for a second time.