For example, when Emperor Seinei, son of Emperor Yuryaku, didn't have a successor, it is assumed that Emperor Ninken and Emperor Kenzo, grandsons of Emperor Richu, succeeded the Imperial throne, but there is also a theory stating that in fact, it was an usurpation of the Imperial throne.
例えば、雄略天皇の子の清寧天皇には後嗣がなく、履中天皇の孫である仁賢天皇・顕宗天皇が王位を継いだとされているが、実際は王位簒奪ではなかったかとの説もある。