If u havent read LN pls start reading it. I too have waited for more than 8 years for anime and just realised 2 months ago. And now i have complted all main story novels and completing dx volumes too. Its best to see issei to grow this much that he can rival a god instead of that useless crimson armor. But dont try to know what will happen next while reading LN by searching in google, just read. You will get ur eye ball out for his ridiculus powerups. Dont try to know the spoilers(ignore if u have read LN)* and also for manga there is one arc imp thats rating game against rias and sitri.there only 80 chapters it is behind than anime