It’s the sequel to Takashi Miike’s remake of the second Yokai Monsters film.
In the 60’s,Daei produced a trilogy of ghost/monster movies. The first,100 Ghosts, is the most like traditional Yokai stories. It features retellings of Yokai myths,and a plot about hauntings.
The second, Spook Warfare, is all about a man possessed by an evil spirit,and an army of Yokai attempting to stop it.
The third, Along With Ghosts has the least to do with Yokai. It’s a pretty straightforward Samurai movie,with some Yokai occasionally popping up.
Takashi Miike directed a remake of Spook Warfare in 2005,called Great Yokai War. It took elements from the other films as well. The Great Yokai War’s plot was all about a corrupted Yokai causing imbalance or something,and a little kid must accept his destiny to become Kirin Rider and lead an army of Yokai.
The new movie apparently keeps the little kid plot from the remake. Daimajin is in the new movie for some reason. I have no idea why,I guess if you stretch you could say he was yokai-ish,being a vengeful magic statue.