Combining classics like "Simple and Clean"/"Hikari," "Dearly Beloved," and "Hollow Bastion," "Dear to My Heart" is an eight-minute ride through Sora's first adventure in the original Kingdom Hearts.
Obviously, this arrangement is an homage to the first game, and it seems to be pulling us right into the climax. The scene it most directly embodies is Sora's confrontation with (the then Ansem-possessed) Riku before the Princesses of Heart are used to unlock the Final Keyhole. After spending the whole game scattered across the worlds, Sora, Riku, and Kairi are physically reunited, but still hopelessly disconnected.
"Simple and Clean" itself is a song about falling apart. This relationship that was once complete and nurturing is now filled with uncertainty, miscommunication, and fear. "Don't get me wrong I love you, but . . ." is an accurate summary of Sora, Riku, and Kairi's friendship in the first game. What was whole is now crumbling. And so Sora reaches this place, this Hollow Bastion, a twisted imitation of something that was once beautiful, and finds his friends - one lifeless and missing her heart, the other estranged and jealous - both so far gone from their time together on the islands.
But Sora, being the optimistic little scamp we've grown to love, knows that his friends are still somewhere in his heart (quite literally, in Kairi's case). After all: "Regardless of warnings, the future doesn't scare me at all. Nothing's like before."