Within the Hagunden (Hall of the Army-Breaking Star / 破軍殿) stands the shrine's innermost and most sacred sanctuary, the Seiōden (Hall of the Star King / 星王殿). The Seiōden is the shinden (hall of the deity / 神殿) of the Hokushin-Jinja (Shrine of the North Star / 北辰神社) and houses the shrine's ancient go-shintai (sacred body of the deity / 御神体), a wooden statue of Hokushin Myōken Sonjō-ō (the Venerable Star King Myōken of the North Star / 北辰妙見尊星王) from the Edo period (1603–1868). As the dwelling place of the deity within the shrine, the Seiōden forms the spiritual axis around which the life of the Hokushin-Jinja revolves.
The name Seiōden (Hall of the Star King / 星王殿) derives from the title Seiō (King of Stars / 星王), one of the honorific names by which Myōken has been revered throughout history. This title reflects Myōken's role as the celestial sovereign of the northern heavens and his identity as the divine embodiment of the Hokushin (North Star / 北辰), the unmoving centre around which the stars and constellations appear to revolve. Within the cosmological traditions of the Hokushin-Shinkō (worship of the North Star / 北辰信仰), the North Star was regarded as the heavenly axis governing celestial order, while the surrounding stars of the heavens performed their eternal movements around it. As the deification of this sacred celestial centre, Myōken came to be venerated as the Seiō (King of Stars / 星王), whose divine authority maintains harmony and order throughout the cosmos. The Seiōden (Hall of the Star King / 星王殿) therefore serves not merely as the innermost sanctuary of the shrine, but as a symbolic representation of the celestial centre itself. Just as the Hokushin (North Star / 北辰) stands steadfast amidst the turning heavens, the Seiōden occupies the spiritual heart of the Hokushin-Jinja, from which the presence and blessings of Myōken extend throughout the sacred precincts.
Unlike the Hagunden (Hall of the Army-Breaking Star / 破軍殿), which was constructed together with most of the Hokushin-Jinja itself in-between 2025 and 2026, the Seiōden (Hall of the Star King / 星王殿) is a historical shrine dating from the late Edo period (1603–1868). Crafted by master artisans of its age, the Seiōden displays the remarkable craftsmanship characteristic of Japanese shrine architecture during the county’s feudal periods. It was built in the traditional Nagare-zukuri (Flowing Roof Style / 流造), one of the most common shrine styles in Japan, in which the elongated front roof is the defining feature. The asymmetrical roof of the shinden in fact extends forward over the entrance, creating a protective canopy above the staircase and approach.
Among the most remarkable features of the Seiōden there are its intricate woodcarvings. Dragons, guardian beasts and clouds emerge from the structural members beneath the eaves, transforming functional architectural elements into sacred works of art. Particularly noteworthy are the carved dragons, whose flowing forms appear to move through the clouds surrounding the sanctuary. Within the symbolism of the Hokushin-Jinja, these carvings evoke Genbu (the Black Warrior of the North / 玄武) in the form of the Kokuryū (Black Dragon / 黒龍), the celestial guardian of the northern heavens and divine companion and protector of Myōken.
The sanctuary is further adorned with carvings of shishi (lion-dogs / 獅子) and baku (mythical dream-eating creatures / 獏), all of which serve as traditional protective symbols within Japanese shrine and temple architecture. The shishi (lion-dogs / 獅子) are revered as guardians that ward off evil influences and safeguard sacred spaces, while the baku (mythical dream-eating creatures / 獏), a legendary creature believed to devour nightmares and misfortune, is likewise regarded as a protector against harmful influences. Together, the carved shishi (lion-dogs / 獅子) and baku (mythical dream-eating creatures / 獏) express the purity of the sanctuary, serving as guardians of both the sacred structure itself and the divine presence residing within.
Through the preservation of the Seiōden a tangible piece of Japan's sacred and artistic heritage continues to endure, connecting the Hokushin-Jinja not only to the spiritual traditions of the past, but also to the generations of artisans whose work was dedicated to the service of the kami (deities / 神).