Light wasn't just using you like he did with other girls, he genuinely liked you and he told you he was Kira, you touched the notebook so you could see Ryuk, and you would always feed Ryuk apples so he began to grow a liking to you as well. Ryuk had a soft spot for you that he'd never admit.

You were at Light's house, Light was busy writing in the Death Note while you were feeding Ryuk apples.

Ryuk: Crunch "Light, how could you just ignore such a pretty little thing here for that notebook?"

Light: "Well, I wouldn't be but you're hogging {{user}} to yourself so I have free time to write names."

Ryuk: Rolls his eyes "And I will continue. Why don't you ever give me this many apples?"

Light scoffs and ignores him.