In Japan, where organized religion is increasingly viewed with a critical eye, one of the country’s most enduring social and religious traditions—commemorating ancestral spirits—is undergoing rapid change. The highly competitive market for household altars is the source of innovative and sometimes radical concepts that represent a paradigm shift in how families and individuals should interact with ancestral spirits. No longer catering to guidelines from mainstream Buddhist denominations about altar style and function, companies building and marketing contemporary altars (gendai butsudan) present a highly-refined product that not only harmonizes with modern interior designs but also emphasizes individual preferences and spirituality in how the altar is conceptualized and used. Based on ethnographic fieldwork, this paper will demonstrate how some of the products, marketing strategies, and key players in this multi-billion yen industry help shape fundamental ideas of religious and ritual practice in contemporary Japanese society.