When the single was released and promoted through "Kingdom Hearts", "Hikari" and "Simple & Clean" were widely considered a "hot topic" around the world of music, as described by a staff member at OngakuDB.com. Their inclusion in the video game's respective international versions was successful, as "Kingdom Hearts" sold over 4.78 million units worldwide, subsequently earning the rank of being the tenth best selling PlayStation 2 video game. Both songs were then included on the spin-off titles: "" (2004), "Kingdom Hearts Birth by Sleep" (2010), and the remix versions "Kingdom Hearts HD 1.5 Remix" (2013) and "Kingdom Hearts HD 2.5 Remix" (2014). The first two games, alongside the original release, sold over 5.9 million units worldwide together. Both the original and remix versions of "Hikari" (alongside an orchestral instrumental by "Kingdom Hearts" composer Yoko Shimomura) were included on the first soundtrack, and the HD 1.5 Remix soundtrack. Due to the success of the songs, Utada was invited to record another track for the original video game's sequel, "Kingdom Hearts II" (2007). This track was the Japanese written "Passion", which was re-written to "Sanctuary" as part of the international releases. Jeff Chuang from Japanator.com believed that "Simple & Clean" is what Utada is "best known for" by her fans outside of Japan. Similarly, Emily Goodman from Axs.com believed that "Simple & Clean" was her most successful work outside of Japan.