The manga will be written by Kamen Rider 555 head writer Toshiki Inoue in cooperation with actor Kohei Murakami, who played Masato Kusaka in the TV series. Details such as the plot and if the series takes place somewhere in the TV series are yet to be revealed. The serialization of the Kamen Rider 913 manga will start on Dengeki Maoh's November issue, which is set for a September 27th release.
[Source: Dengeki Hobby Web]