User blog comment:B214/High School DxD EX/@comment-26439090-20150708071843/@comment-26209278-20150708095956

They're six side stories that are being released with the six Blu-Ray discs of the 3rd season (one with each disc), and each story will be about one of Issei's children (I believe, not sure about that). Either way, the SS's are about his children.