Also known as "Sanctuary" by English-speaking fans, "Passion" is Utada's second gift to the series, notably replacing "Simple and Clean" as the main theme for Kingdom Hearts II. Kyle Landry's arrangement, first released in 2003, has become a fan-favorite among his uploads and reappears as the finale in his Kingdom Hearts medley.
"Passion" and "Sanctuary" are both love songs, be it romantic, platonic, or both.
"In you and I, there's a new land . . . Where fears and lies melt away."
When you're with this person (or these people), you're safe. You're home. They are your sanctuary.
This is illustrated perfectly by KH2's ending, one of the only happy ones of the series, in which Sora, Riku, and Kairi are finally reunited on Destiny Islands. A new version of the song, subtitled "After the Battle," plays as they feel secure and complete for the first time since their journey began, back before keyblades, and heartless, and the darkness. Nothing is the same. They've changed. The worlds have changed. But they still have each other, and that's all they've ever needed.