I’ve been noticing that in my headcanons Asmo and Satan share a lot of traits and stuff.
Like I think Satan picked up certain mannerisms or personality traits from his brothers over the years, not purposefully, it just kinda happened.
He places his hands similar to Lucifer, gesturing subtly as he talks. Like mammon, he rubs the back of his neck when nervous. His love and passion for books, cats and mystery parallel that of Levi’s for anime and TSL. When he started to become his own demon, something more than wrath, he practiced to smile like Beel. And all that mischief and pranking directed towards Lilucifer is Belphie’s doing.
There’s small things he does like his brothers, I mean, they all practically raised him. And while it was said in game that Lucifer “took control of the controller” the most when it came to Satan, I think Asmo was also up there at least top three (I think Mammon took care of things often too if Lucifer wasn’t able to).
Asmo was the first to get (familiarly) lovey dovey with Satan, doting on him and treating him as another family member, painting his nails like with everyone else, hugging him (which Satan hated at first, but over time came to accept and return), bleaching his hair for him and asking for his opinion on an outfit or hairstyle (strangely makes Satan feel like a proper older brother). It was only a matter of time until picked up on Asmo’s mannerisms and such.
For example: gossiping. At first to try and get dirt on Lucifer (which he still tries to do, especially for the RAD newspaper with Mephisto), but eventually came to like chatting shit with Asmo. Particularly when painting nails or bleaching hair.
Sometimes if you past Satan’s room, you can hear a soft humming from inside. Wether he’s reading, or studying, or feeding a kitty he managed to hide from Lucifer (for now), he’s often humming a soft little tune to himself, similar to Asmo when he is doing his hair or makeup, or painting the brothers’ nails.
I think Satan is just a collection of all his brothers, he loves them (even if he doesn’t want to admit it) and his entire being is the proof of that, carrying them with him always in the way he does small things.