Las vacaciones de verano se acercan rápido para Hyodo Issei, ¡pero sus planes quedan suspendidos al enterarse que debe acompañar a Rias al inframundo para su visita a casa! Una nueva aventura está por comenzar y, mientras, Koneko está actuando extraña.

Issei and the others start their training to improve their skills; Powerful people gather to fight against the Chaos Brigade.

Koneko's sister Kuroka has taken her sister away from Rias Gremory; Issei and Rias chase after her; A figure appears at the great gathering.

Loki has been temporarily sealed away; Odin returns North to retrieve the powerful hammer Mjolnir.

Rias and her household return to the human world to finish up their last days of summer after Loki is defeated; Issei forgoes homework to go on a date with Akeno.

Issei and the others are back to school and their daily lives. Irina and Rossweisse both start to live at Issei's house and the sports festival is fast approaching. During all of this, Diodora Astaroth appears before Asia and proposes to her?!