What's the secret to the manga SPY×FAMILY's popularity? Its overwhelming readability, the high level of artistry, the easy-to-grasp setting and story, and their depth — those all play a part, I'm sure, but the biggest factor is surely the popularity of its charming cast, starting with Anya. The fact that character merchandise keeps pouring out is proof of that. And it became even more pronounced once it was animated. The voice actors' superb performances breathed even more life into the characters, making their charm easier to convey, and that's what I think turned SPY×FAMILY into a nationally beloved anime.
What lends these charming characters' emotions and the world's setting their persuasiveness owes a great deal, above all, to the power of the soundtrack. I've written about the SPY×FAMILY anime soundtrack before, but the familiar music is of course used in this film, CODE: WHITE, too — and that music, brimming with loving, playful homage, once again has the power to fill the viewer with excitement. Of the music newly used in this film, the part I found especially amazing was the scene right at the beginning, when the train the family is riding arrives in the Frigis region. The music — blending the crisp air unique to a cold, snowy region with the elation of arriving at a travel destination the moment you get there — makes you feel, just by listening, as if you were aboard that train alongside them, gazing at the same scenery. I live in Hokkaido, so I'm sick to death of looking at snow, but I do feel that chilly yet dignified air on my skin every day, and I'm well aware that the thrill of traveling is something irreplaceable no matter how old you get.
I don't particularly want to go somewhere cold, but I couldn't help imagining how, if someone who normally never sees snow came to Hokkaido on a trip and heard a melody like this soundtrack — the chime of bells, a beautiful high violin, a harp and flute, playful yet refined — the emotion would be even greater.
The Celtic-flavored soundtrack that plays at the Rubble & Bonds tavern is the real deal, and it fits the shop's exterior perfectly. There's a romance packed into music that uses old shops and old instruments. In the scene where military personnel storm the restaurant and snatch away the Meremere (an original sweet that appears only in this film — incredibly, when I Googled it, there are even people who created reproduction recipes based on its appearance alone, which is amazing), there's tension, but also a wealth of film-music technique scattered throughout. The dizzyingly shifting developments early in the film are crafted so that, thanks to the soundtrack's persuasiveness alone, the scenes and emotions click into place in an instant.
This may seem like a change of subject but isn't, really: the townscape you see in the market-like scene in the Frigis region looks very much like the special venue at the Munich Christmas Market held in Sapporo every year from November through Christmas, and when I heard the soundtrack playing in that scene, I felt, "Ah, this is the right answer." Sapporo and Munich are sister cities, and although I knew their climates and such were similar, I've never actually been to Germany, so I could only imagine what kind of place it is — but this soundtrack's overwhelming persuasiveness stuck with me, and I oddly found myself convinced it must be a lovely place where music like this would naturally drift through the air. (SPY×FAMILY is set in a fictional world, but its model is said to be Germany.) There were many more wonderful soundtrack pieces beyond this scene, but if I explained each one I'd end up spoiling the entire film, so from here on, please go watch and enjoy the movie for yourself. It's very SPY×FAMILY — satisfying for fans and easy to get into for newcomers — so I highly recommend it!

Cited from the official site https://spy-family.net/codewhite/