Moronobu had been successfully promoted from Kurodo no to (Head Chamberlain) of the Emperor Gouda, then Sangi (councillor) at the age of 17, then Gon Chunagon (provisional vice-councilor of state) in 1299, and then Gon Dainagon (provisional chief councilor of state) in 1303.
後宇多天皇の蔵人頭から17歳で参議、正安元年（1299年）に権中納言、嘉元元年（1303年）に権大納言と順調に出世を重ねる。