[She's lying, or at least covering something up. Which makes him worried, because Rin only ever covers up big things that she doesn't want to talk about. If it were a little annoyance, she'd say as much.]

I can tell you're not being honest, you know.

[But. But. He's going to leave the call-out at that. Demanding answers never works well, since Rin always either clams up entirely or starts yelling at him when he badgers her.]

...But if it's nothing you want to talk about, that's okay. So long as it's nothing dangerous.