Almost from the moment she sees him Lucy seems to have a good feeling about the "pleasant" faced Mr. Tumnus. Lucy accepts his invitation to go to his house without hesitation, taking his arm "as if they had known one another all their lives."

Lucy loves Mr. Tumnus's house. Like Mr. Tumnus himself it has a kindly, welcoming feel that puts her at ease. It is only when he starts to cry, telling her what a bad faun he is and how he had planned to kidnap her, that Lucy becomes disturbed. Even then, however, Lucy is able to empathize.

I don't think you're a bad faun at all. I think you are a very good faun. You're the nicest faun I've ever met.

Arguably Lucy's second visit results in the White Witch arresting the faun and turning him into stone. Lucy feels so bad about it that she makes it her mission to rescue him.

Beyond telling her siblings that Mr. Tumnus is a "nice faun," she doesn't really elaborate on her reasons for liking him. However, there seems to be an unexplainable attraction between them. Both feel at ease in each other's company and can instinctively emphasise with the other's plight.