As Emperor Reizei was mentally ill, there was an urgent need to install a successor; Imperial Prince Tamehira, his younger brother from the same mother, was a front runner for Crown Prince.
冷泉天皇は狂気の病があったため、早急に後嗣を立てる必要があり、同母弟であった為平親王は東宮の有力候補だった。