an “I Understand You” moment: a moment that makes her say, almost despite herself, “Oh, look, there’s a bit of kismet here, maybe we should be together.”
You can see him endeavoring to do this in his feigned “chance encounter” early in the movie. She is on the bleachers reading, so he just happens to choose the same bleachers for his own reading. He wants to seem to be a serious, thoughtful adult like her, so he gets out from the library “The Powers That Be” by David Halberstam, a forgotten icon of parlor-room intellectuals of a generation before. He’s hoping she’ll say, “Wow, this is no kid, this is a serious adult like me, and I’ve just met my soulmate.” But of course, it doesn’t work. He’s no adult, and it’s not going to happen.
Max finally meets a real romantic prospect towards the end of the film. At first, he sees that Margaret Yang is drawn to his energy, as many kids are, and so he uses her in his play without taking her interest seriously, ignoring her when she comes to his house. It’s only later, in a chance encounter, that he realizes that this is a kindred spirit.
He’s flying kites with his acolyte Dirk, only to discover that Margaret is flying her remote control plane in the same field. He then sees that she has made an adorable flight plan, much like the kind of thing he would make. That’s the “I understand you” moment, but what happens next really seals the deal: he finds out that she almost defrauded the navy into buying a science project that she faked. She is more mature and compassionate than Max, but she is, at heart, a dreamer and a schemer just like him.
For practical reasons, Margaret is the only real prospect for Max in the movie, but she can’t just be “the love interest” or else we will reject her. We the audience must decide for ourselves that they belong together, preferably before Max does. That way, we get the thrill of watching our hero belatedly make the right romantic choice, fulfilling our desires, not just his own.
An “I understand you” moment will sometimes consist of one character entreating another for love and proving his or her case, but just as often, it sneaks up on both characters, unexpectedly proving to the both of them that they belong together (In this case, before he’s ready to hear it, and after she’s already given up.)