Armin Arlert isn't very smart. He doesn't need to be. You don't need to know things when you're in love, and he's insanely, irreversibly in love with his best friend, Eren. And he's only thirteen, and later he will question if it's just that he loved the idea of being in love, because when you're thirteen nothing really counts anyway. But that's not important right now, because he's convinced himself that he's in love, and everything is perfect. And even if he's sure that Eren doesn't love him back, that's okay, because Armin has perfected the art of loving unrequited. (I do not own any of the Attack on Titan characters, etc.)