 In his old age, Tenji had a son, Prince Ōtomo, by a low-ranking consort.Since Ōtomo had weak political support from his maternal relatives, the general wisdom of the time held that it was not a good idea for him to ascend to the throne, yet Tenji was obsessed with the idea.In 671 Tenmu felt himself to be in danger and volunteered to resign the office of crown prince to become a monk.