Wide and Deep Exploration of Radio Galaxies with Subaru HSC (WERGS). IX. The most overdense region at z ∼ 5 inhabited by a massive radio galaxy. - Uchiyama, Hisakazu; Yamashita, Takuji; Nagao, Tohru; Ono, Yoshiaki; Toshikawa, Jun; Ichikawa, Kohei; Kawakatu, Nozomu; Kajisawa, Masaru; Toba, Yoshiki; Matsuoka, Yoshiki; Kubo, Mariko; Imanishi, Masatoshi; et al. (Publications of the Astronomical Society of Japan, 2022)