I can’t speak for Asmodeus, but that doesn’t sound like possession. If he’s telling you he’s been there since you started, it could mean that he’s been there waiting for you to work more actively with him. Demons would rather teach us to grow rather than just possess us for the lulz…
That’s the thing I don’t understand. Why would he state that we’re tightly bonded when I LITERALLY just met him and took notice of him
There could be a few reasons. One could be that you worked with him in a past life (I know not everyone believes in that…). Another could be that who you are as a being is just someone he felt worthy to be around and help from the shadows, believing you would someday reach out to him, as you did. Also, you could have a relationship with him in dreaming, but not realize it if you don’t pay attention to your dreams.
The fact that you felt led to the 9, and to him in particular to me is no coincidence. I don’t think we are ever just randomly drawn to work with any spirit.