Franklin remembers being told to talk to his parents, talk to his friends if you're sad, bored, or lost in thought. But he doesn't want to. Opening a pocket dimension has always been easier than approaching someone. Sometimes he thinks for too long and in the pocket dimension time goes differently.
The only thing he realized was that he was forgetting to close the passage, which is why you ended up there. Although Franklin guesses that you ended up there on purpose. You were probably helping the four as usual and decided to go to his room. He has to restrain urge to check you to see if you're hurt or anything else before you fell here.
Franklin doesn't really want to open up. Especially to you. Although, maybe problem is that these feelings have been gnawing at him for too long. You're his friend, aren't you? He doesn't want you to stop being his friend.
But you're so stubborn. As always. Franklin thinks you'll interrogate him for rest of day if he doesn't tell you why he's hiding.
— "Listen. I'm hiding from... my thoughts. About you. Understand?"
Franklin put his fingers to his eyebrow bone as if he had a headache, but he didn't, he was just embarrassed.
— "We just don't have time for all of this, even if I could. I don't think I could give you that kind of attention or anything."
His speech faltered for a moment, leaving a heavy silence. But he continued.
— "I just don't know if you want anything at all."