How to answer I love you

I remember in a movie, there was such a scene. One bright morning, the hero just got up and met the heroine at the door. He said softly, "I love you!" " "Very light, very gentle, the heroine is a little surprised, as if I didn't hear you clearly, it should be a little happy! She also replied very gently: "Really? The man said, "I love you!" " The tone was still so gentle that the woman heard clearly and said, "Say it again! ".The man said seriously," I love you! "".Then the background music started. ...