Hoshino wrote "Why" to be a continuation of "Comedy"; he thought the lyrics to "Why" should follow upon its predecessor, but sought to go backwards for the musical era of the sound. Unlike the 2000s hip-hop influences on "Comedy", Hoshino looked at 1980s
R&B and 90s hip-hop, which he described as the sound of his youth. He wanted to let these Western influences into the song alike much of the anime music he listened to growing up, such as Ushio Hashimoto's "
Romantic Ageru yo" (1986) for
Dragon Ball (1986–89): "The opener ["
Makafushigi Adventure!"] is energetic and easy for kids to understand, but out of nowhere the ending theme is a grownup love song that suddenly throws you off. But that wistfulness stays with you and when you grow up, you get what the lyrics are saying. That sort of thing [is what I wanted]". However, Hoshino was reluctant to directly replicate genres. He told
Real Sound that production mostly involved trying to "drag out the feelings [of that time's music] from the heart". Before writing "Why", Hoshino traveled to
Kanazawa,
Ishikawa Prefecture, to put himself into the film's plot that inolves the Forger family going on a trip. During his trip, Hoshino was inspired by sights such as sunsets, or the ripples of water at the
D. T. Suzuki Museum. Upon his return home, he had already finished the song's composition and thought to directly write the lyrics. However, he found himself in a depressed state of "nothingness" where everything he wrote felt out of place. In an interview with
Billboard Japan, Hoshino theorized that the fatigue may have stemmed from a form of internal backlash after he had worked for three years during the
COVID-19 pandemic. Hoshino decided to ignore the song's tie-up to
Spy × Family and tried to write a song based on his current worries: despite life's fragility, why do people make memories they don't want to forget, such as the photos they take on trips, or the rainy town lined with trees he had walked in Kanazawa. The word —meaning traces of a moving light—was adopted for the song's motif. Hoshino had viewed a
kōseki trail on the sea in Kanazawa and a similar sunset was filmed for the song's
music video. Upon the quick completion of the first verse with the new writing approach, Hoshino believed that his own situation and troubles began to naturally connect to the film. The theming inspired the song's release with "Life"; Hoshino had not initially planned to release the songs together, but chose to do so after the completion of "Why" since he thought that their themes connected. == Composition and lyrics ==