Defspiral, a Japanese visual kei alternative metal group formed in 2010, originated from the former members of the Underneath, with vocalist Taka, guitarist Masato, bassist Ryo, and drummer Masaki initially. Their breakthrough came with the single "Dive into the Mirror" (2010), which served as the opening theme for Kamen Rider: Dragon Knight, followed by "Twilight" and "Revolver" (2010) under Avex Mode and Knowledge Alliance/PCI Music. The band’s debut album, Progress (2011), showcased a stronger musical style and was released by Plug; it was succeeded by Voyage (2013) and Brilliant World (2015) on Sonic Scope. Notable singles include "Break the Silence" (2012) and "Glare" (2013). Defspiral collaborated with the Kamen Rider series, contributed to the maxi single Reply –Tribute to hide– (2011), and performed the theme "Leave all Behind" (2010) as Wilma‑Sidr. After a decade of activity, drummer Masaki departed in 2021, and Kazuki joined in 2022, marking the latest lineup change. The group’s releases have consistently appeared in the Japanese rock charts, and their work on Kamen Rider soundtracks has solidified their presence within the visual kei and broader rock scenes.