Yo, I was just wondering, if you could tell me; in Red Dragon of Chaldea, you stated that issei was betrayed by the factions, his harem, and vali. I was really wondering what type of reasoning they had for doing so.
Actually, I did have an idea about it. Basically, Issei a little bit more mature just a simple dragon who loves challenges, together with Ingvild. Both separate from the political stuff of the devils. After making Rias the rating game champion. issei saw this as him completing his task. Now he follow as his own ideals to make a harem and to have fun! Then would go to little garden and have a friendly rivalry with izayoi.