User blog comment:HollowIchigo58/High School DxD Season 4 Announced/@comment-50.139.232.230-20161025045141/@comment-26345952-20161025105400

For the main plot, maybe. But at the same time it does gives us a backstory on how Sirzechs and Grayfia met, a bit of world building, and also shows that Rias can't get away with what she did without any consequences. A point in Vol. 5 that I liked that BorN omitted.

Even so its main points were to give us a Issei x Rias moment, Issei vs. Satan Red and the most important, Ajuka adjusting Issei's EP.

Also, it is with that short story that Issei tries to bend the Dragon Shots, inspired by Sirzechs control over his Power of Destruction.