Looking at the shrine’s kami, the originally enshrined ones were the five beginning with Emperor Ōjin; the three beginning with Sumiyoshi Ōkami came next, and the three beginning with Uga-no-Mitama were added in the Meiji Period. Note that Emperor Sudō does not appear in the official list of emperors.  In life he was Prince Sawara (早良親王, 750-785),  the fifth son of the 49th emperor, Kōnin  (光仁天皇, 709-782); in 781 the latter abdicated in favour of his son, Yamabe, who became Emperor Kanmu, and  named his younger brother Sawara as crown prince.  Political problems followed, however, and after being exiled from the capital Sawara died, possibly of self-induced starvation. After his death he was given the title Emperor Sudō. I think this is the only example of someone being named emperor posthumously. ​Prince Iyo-Shinnō was one of Emperor Kanmu’s 36 children and hence a nephew of Prince Sawara, and, like his uncle before him, met an untimely death. His mother was Fujiwara Yoshiko (藤原 吉子), and having got caught up in intra-Fujiwara clan machinations mother and son were accused of treason and allowed to commit suicide in December 807.  

In the grounds of the shrine there are many large rocks, perhaps the most notable of which is the one directly behind the main hall (unfortunately I either failed to take, or have since inadvertently deleted, a photo of it: there is such a photo on the shrine’s home page).  It is considered sacred and is known as the Kamagura (clam, 蛤) Rock. The name derives from a local inhabitant once having picked up a clam from the top of the rock, thus gaining happiness, prosperity, and a long life (福徳長寿)