The requirements to be granted Ippon were that the prince must be in nihon (the second court rank for imperial princes) over 20 years through the Nara period to that time, if the period being in nihon was less than 20 year, the prince must be Shikibukyo (Minister of the Ministry of Ceremonial), the highest post for an imperial prince for a long time as well as holding appropriate career as the 'first Imperial Prince.'
奈良時代からこの時期を通じて、二品親王の地位に約20年以上いること、それ以下の場合には親王が就く官職で事実上最高位であった式部卿を長期にわたって務めて「第一の親王」たるに相応しい経歴を保持していること。