An official record of the time states that 'Naosuke II had a sudden illness and, while struggling with the disease, he submitted a request for his succession, which was accepted shortly before his death.'
当時の公式記録としては、「井伊直弼は急病を発し暫く闘病、急遽相続願いを提出、受理されたのちに病死した」となっている。