These are based on the belief called 'jyuoshinko' in which the dead should receive ten judgments, from each of the ten kings of the realm of the dead, on ten specific days consisting of eight kinichi (specific days after death) of every seventh day starting from the shonanoka (the sixth day after the death) until the shijukunichi (the forty-ninth day after death), Hyakkanichi (the one-hundredth day after death) and two nenki, the isshuki and the sankaiki.
これは、亡者が「初七日」～「七七日（四十九日）」と「百ヶ日」を含めた8つの忌日と、「一周忌」、「三回忌」の2つの年忌の、合計10度の時点で、冥界の十人の王に審判を受けるという「十王信仰」に基づいている。