This article analyzes how the Modern Mystery School (MMS), a transnational business specializing in Western esotericism, has adapted to Japan’s spiri tual landscape over the past two decades. Specific beliefs, practices, and social structures have been dialectically constructed at the West/East interface. Secret teachings in the lineage of King Salomon and Jesus Christ, closely aligned with the Hermetic Order of the Golden Dawn and the Theosophical Society, are now innovated in Tokyo and adapted to the Japanese marketplace of spiritual thera pies. Although developed in Scandinavia and North America by the Icelandic founder Gudni Gudnason, the transnationalism of MMS calls into question the strict reification of Western esotericism. While MMS teachings promote a diffu sionist model of Western esotericism as radiating to the East, the ethnographic picture is more complex. The innovations made by Founder Gudni to localize MMS cosmology in Japanese geography, and the agentive role of Japanese fol lowers, are placed in the context of a group that is irreducibly both a for-profit business and a “spiritual path.” MMS remains one of the largest and most stable spiritual seminar companies in Japan. This article draws on fieldwork conducted between 2021–2023 with the permission of MMS leaders and consent from all interviewees in accordance with ethical standards for qualitative research.