Frisk does not know Sans is there. Normally, they'd at least suspect, but walking through the hallways they were killed in less than what feels like a couple hours ago kind of drove a lot of...everything else out of their mind.

So they don't look back, or anywhere else but at Chara.

...Right. They have no idea what Frisk's name is, do they? Maybe they'll learn it later.

They aim a thumb at their face. "Me. Can we talk?" they ask plainly. "Or...still think this stuff is all my fault?"