Hina asked if everything is a lie, and he said, no, it’s an experiment. Thanks to that, he knows her reaction if someone dies.
So everything had been a lie – he set her up to collect all sort of data about her. She cried, feeling betrayed because she really did worry him.
He then wondered if he should really die in front of her to get her reaction, and get someone else to record the data. She then snapped and told him off for this. Angry, she ran away calling Remu an idiot. He was confused on why was she angry.