The basis that Tomoko was a wife of Emperor Koko is that Tomoko, who had no rank at that time, was ranked Jugoinoge (Junior Fifth Rank, Lower Grade) on March 30, 884 right after the accession of Emperor Koko, and Princess Hanshi (her father was Imperial Prince Nakano, son of Emperor Kanmu), who was a nyogo (wife) of Emperor Koko and the mother of Emperor Uda, was ranked Jusanmi (Junior Third Rank) ("Nihon Sandai Jitsuroku" (sixth of the six classical Japanese history texts)).
類子を光孝天皇の後宮とする根拠は、当時無位であった類子が、光孝天皇践祚直後の元慶8年（884年）2月26日に従五位下に叙し、同日に光孝天皇女御であり宇多天皇の母である班子女王（父は桓武天皇皇子仲野親王）が従三位に叙しているからである（『日本三代実録』）。