User blog comment:Piyush Banerjee/Shin DxD 2 discussion/@comment-33939194-20190212130232/@comment-33939194-20190214034213

Actually there are some references. The climax of the rating game between Issei and Rias took place on the school roof. The same location where the climax of the game between Rias and Riser took place. Also there's the whole fighting for one's future. In the original vol. 2, Issei was fighting Riser for Rias future due to Rias was in forced engagement. In Shin volume 2, Rias is fighting Grayfia for Issei's future due to Grayfis trying to force a future on Issei of him becoming a Maou.

Lastly the game ended in a strategic sense. Issei beat Riser by coming up with countermeasures and exploited his weaknessess. Issei beat Rias by exploiting her weaknesses through the usage of dressbreak of Nyuutron beam canon.