*sigh, I can only say is pathetic. Just from reading this I know at least 25% of the story, its starting to get common. Mc gets reincarnated in dxd, train hard, interact with a devil, have relationship with the devil faction. I don't know if the mc is dense or arrogant just because he knows the plot in the story. He should remember he is going to interact with devils which is also manipulative, arrogant, giant poles one their a**. It would be best for me, to create your faction the throne of heroes which consists some descendants of heroes or you summon some heroes. Really, its like you are giving the devil advantage where they make a deal and you think about it then you agree and back to the plot. I am also guessing you met the trash (issei) you train him, you became weak because of attachment and only become strong because of the power of friendship/ or you just reveal your true strength when someone precious injured or die because if the mc ignorance.
People wanting to read DXD fanfic without main characters in it is just plain stupid. It's the characters who make DxD so likable. DxD is not DxD without Rias and Issei and others. You people might as well read original rather than DxD fanfic.
you don't say 'indefinite potential' because indefinite is only used as a duration of time. In this case it'd be infinite potential.
Also, there's no way the Gremory have Gravitational zones like Jason does. Just look at their training resort, 0 training equipment. Jason just agreed to align himself with Gremory for absolutely 0 profit on his side while the Gremory will be able to brag that they got 2 powerhouses to train/spar with their heirress.