Soul Imprint

"Why the hell are you idiots sulking now?" Ashton asked his summons. 

The subconscious of the summons was connected with Ashton's. Technically, their subconscious was linked with [Valhalla], the domain Ashton used to store his undead summons, and since Ashton was the owner of the domain, their subconscious was indirectly linked to his own.

That's why his summons could also feel whatever he felt or did. Even emotions like love and care could be felt by them. Through this connection, the summons knew how important Anna was to him when he started having feelings for her. 

Around this time, they realised that Aegis had gotten closer to their master's heart even though he hadn't served him for a single day; they began moping. Well, most of them did, except Atlas and Raven.

While Atlas didn't give a fuck about Ashton's personal life, Raven wasn't bothered by Ashton's affection towards Aegis because he knew he was nothing more than a servant to Ashton.