Oimatsu Shrine is located just off the main road running through Sasaguri, northeast of Fukuoka. I visited at sunrise on the second day of my Kyushu pilgrimage.
At the entrance stood a massive, old Camphor tree almost 10 meters high. Many of the shrines in this area have big camphor trees, though this one also had a cedar tree whose trunk had divided into two.
Though it is not called a Tenmangu, the kami enshrined here is Sugawara Michizane, known sometimes as Tenjin. There are a lot of Tenjin shrines in this area which is not surprising as it is close to Dazaifu where Sugawara was exiled and died.
There was also a small sumo ring in the grounds. In some areas of Japan shrines will have a sumo ring, and in other areas they won't. Not sure what the deciding factor is or was.