Bianca was left alone with Amon while Barbara was allocated by Bianca to a secret room in the restaurant where she would be able to help her stabilize her evolution, even help her progress a little further.
Amon also needed to stabilize his current power, but Bianca only had one room, and he didn't come here for that purpose. Initially, it was just to pay a visit. After all, he needed to at least develop his relationship with Bianca a little. Since he decided to have her stay, Amon compromised.
This wasn't only out of responsibility: Although he didn't understand love very well, he cherished her and even dreamed of her. It wasn't strange that he was interested in seeing her.
Bianca's eyes never turned from Amon. Seeing him look at her so passionately, it made her happy, especially seeing that even with just a few gestures and words she was able to have an effect on him...