[Vampires have a very good sense of what is around them. Heightened senses and all that. So he knows almost immediately when someone appears in the apartment. Knowing that Sherlock is still in the hospital, Subaru's entire body tenses. He certainly didn't invite anyone in and most people knew Sherlock is away..so this means it is some kind of intruder.

Subaru spends most of his daytime hours inside since the sun makes him feel weak. He doesn't die like the vampires in some myths, but it certainly isn't as refreshing as it might be for some. So instead he either naps in the quiet of the day, or takes the time to clean the home. Today he had chosen to clean and was doing so in the room he had been given. This has all been interrupted now, however.

Eyes change to a nearly glowing yellow color as those vampire abilities activate. He's ready to defend their home if he needs to. Stalking the prey, he moves silently down the hall until he can see the main room where the intruder is standing.]

Who are you and why are you here? [The tone is rather no-nonsense as he keeps his distance, still keeping to the shadows of the hallway.]