For season 2, a big theory of mine is that we will see Mephisto III's detective side looking into Ichiro's past. After seeing the events of episode 12 with Ichiro surviving by becoming/is already a demon/hybrid of some kind and all of the events with Strophaia- I think Mephisto would want to know more about his partner. I think it would come back to that cult they mentioned in episode 7, where Ichiro's human parents abandoned him as a sacrifice for cult, only to get taken in by The Count as the reincarnated vessel for Aeshma or some other pure evil.

The main way of the characters finding out these things is with a reincarnated/reborn/weakened Strophaia who is willing to go along with things if it means protecting Aeshma. He would still be a freak and naughty, but weakened due to Solomon's Flute and learning emotions alongside Aeshma/Ichiro. I think the Millennium Kingdom can only truly be obtained if Humans, Demons AND Angels can live together in peace. Strophaia included.

The season 2 big bad would either be The Count or Ichiro himself. It would be really cool if after his heart being ripped out, the Aeshma side of his mind slipping control again. He has a heart, he knows emotions like grief and sadness now- but Aeshma is Wrath, and what happens when he feels wrath...?

So basically I want corrupted Ichiro.