Japanese religious practice around death draws on two models of what happens to a person that are, considered abstractly, difficult to reconcile, and the fact that ordinary practice holds both without much strain is itself a notable feature of Japanese religious life.
The Buddhist model, imported from the continent, holds that a person is reborn according to karma into one of several realms or achieves liberation from rebirth altogether; the elaborate sequence of Buddhist memorial rites at fixed intervals after death, the forty-nine-day period, the first anniversary, and further anniversaries extending in some lineages to the thirty-third or fiftieth year, is built around aiding the deceased's passage through this process. The indigenous pattern, by contrast, holds that the dead gradually become ancestors who remain in ongoing relationship with the household and eventually merge into a collective ancestral presence, with no reference to karma or rebirth at all.
In lived practice these are treated less as competing metaphysical claims than as complementary vocabularies addressing different aspects of the same transition: the Buddhist framework supplies the ritual calendar and the posthumous Buddhist name (kaimyo), while the indigenous framework supplies the ongoing emotional relationship a household maintains with its dead, visiting graves, maintaining a home altar, welcoming ancestors during Obon, largely independent of whatever realm a temple's doctrine says the deceased occupies. Scholars generally treat this coexistence not as inconsistency but as characteristic of how Japanese religious life layers distinct systems for distinct practical purposes rather than requiring one reconciled doctrine.