After the death of Imperial Prince Hachijo-no-miya Naohito who had no heir in September 1689, Saku-no-miya became the heir of Imperial Prince to succeed to the Miyake (house of an imperial prince) as designated by his father (the Emperor) in November of the same year, and was granted the Miyago (reigning name) of Tokiwai-no-miya.
元禄2年8月八条宮尚仁親王が継嗣となる王子のないまま薨去したため、父帝の命によって、親王の継嗣として同年10月宮家を相続し、常磐井宮の宮号を賜る。