User blog comment:B214/High School DxD EX/@comment-24053170-20160113224250/@comment-79.31.174.119-20160114001050

Issei has more than 20 children, even if Ophis could have childrens maybe her and Issei's children is one of the kids who is not a fighter or who is not at the age and at with the strenght necessary to go on this mission.

The number of childrens of Issei that are fighter and no-fighter is balanced. And the only ones who travelled back in time are the ones who are fighter and old enough, so...