Speedstar Records released it as a digital single on April 27, 2021, and later reissued it as a double A-sided CD with the song "Create" on June 23, 2021.

He took inspiration from anime, novels, and synthesizer-heavy R&B music from the 1980s to write a heartaching song; he penned and produced the track alone, and arranged it with collaborator Mabanua.

A love song, "Fushigi" is an analog synthesizer-driven J-pop ballad with elements of funk, R&B, soul, and urban contemporary music.

Hoshino performed "Fushigi" at various events, including the 72nd NHK Kōhaku Uta Gassen on New Year's Eve 2021, and featured it on his Reassembly tour in 2023.

From his third album Stranger (2013), he began to incorporate greater use of synthesizers and string arrangements,[1] but continued to compose songs with the guitar.

[8] Hoshino viewed the offer as an opportunity to write a love song with intention, describing his previous attempts as unintended results.

[13] Emi Sugiura, writing for Rockin'On Japan, described the sound as "unrestrained", progressing from a generation of J-pop music that had prioritized universality.

[14] It was announced that Hoshino would perform the theme song to Why I Dress Up for Love on March 30, 2021, but further details were withheld until its appearance on the show's first episode, broadcast on April 20.

[23] "Fushigi" was re-released by Speedstar as the lead track of a double A-sided CD single with "Create" and two B-sides on June 23, 2021.

[24][25] The support of 136,665 first-week CD sales from the double A-side helped "Fushigi" rise to the number one spot of the Japan Hot 100 chart dated June 30, 2021.

[29] When it later climbed to number one of the Hot 100, Kurimoto opined that the song has a subtle quality – as opposed to an overtly catchy melody – which he thought helped it achieve longevity on the charts.

Azuki Ogiwara for Real Sound wrote that the text has the "warmth of human skin",[13] and Rockin'On Japan's Emi Sugiura believed that Hoshino managed to create a J-pop song more personal than the norm by setting out to express the difficult yet important concept of romance.

[38] To commemorate the announcement of the song's release, Hoshino opened an official TikTok account where he posted footage of when he completed the track in a recording studio.

He gave its debut performance via a ninety-minute special of Count Down TV on June 7, 2021,[46] and sang the song from the Tokyo International Forum for the 72nd NHK Kōhaku Uta Gassen on New Year's Eve.

[47] In March 2022, "Fushigi" served as the penultimate closer to Hoshino's second Enkai online concert, where it was arranged in a band sound.

[52] In April 2023, an acoustic arrangement of "Fushigi" appeared in a commercial for Kirin Brewery's Green Label product line of beer.