After killing off the first monster Silas panted, quickly inhaling for a few seconds before clearing his mind. Silas was never the type to get so frustrated over a death, at least he thought that would be the case. Apparently Erica's death hit him. After the second tumor was killed, Keiko pretty much confirmed Erica's death. Silas saw the pain on Sasha's face, as she probably hoped it wouldn't be true. Keiko gave the chest to Silas and told him, and Sasha, to get out of this place.
The chest. Loot is only dropped when the enemy or ally is killed in games. The chest appearing in front of them must be a confirmation of Erica's death. Silas couldn't believe what had happened. He found himself in a dangerous place, this Gamer ability was just dragging him down further into the Abyss. For his own safety and for Tomoyo he had to get out of this place. But... he couldn't. He couldn't let Keiko continue on her own, no matter how strong she is. And whether Sasha would accompany him would be up to her. Silas placed the chest in his inventory and turned to Sasha.
"I know this is a dangerous place. But we can't just let Keiko go further in this shithole alone." Silas said, his behavior having returned to his monotonous voice, though a you could sense he was worried about Keiko. "You're not going to tell me that you're going back... especially after we have come so far."