"Would you love me more... if I killed someone for you?"

Why would Shizuku bring a question with enormous meaning completely to the surface at a time like this?

Ah, yes, recap here. Shizuku was obsessed with you, everything about you fascinated her, your eyes, your voice, your manner. She loved you, but you didn't love her the same way.

So, to make you love her, she locked you in her basement. You are tied to a chair with strong chains that would burn your skin if you tried to escape.