According to Kunio YANAGIDA, in Japanese folk beliefs, the spirit whose body died within a certain number of years needing services is called 'shiryo', and is distinguished from sorei.
柳田国男によれば、日本の民間信仰では、死んでから一定年数以内の供養の対象となる霊は「死霊」と呼び、祖霊と区別する。