Shiina has often collaborated with his sister Ringo Sheena by singing duets together, most notably the theme song of the Mika Ninagawa directed film Sakuran (2007), "Kono Yo no Kagiri".
[8] The siblings both released cover albums in May 2002: Junpei Shiina's, Discover, featured a cover of Roberta Flack and Donny Hathaway's 1972 duet "Where Is the Love" sung with his sister, while Ringo Sheena's, Utaite Myōri: Sono Ichi, featured the pair dueting Marvin Gaye and Tammi Terrell's "The Onion Song" (1969).
In addition to his sister, Shiina's album Discover featured collaborations with rapper Twigy, members of Tokyo Ska Paradise Orchestra and singer-songwriter Daisuke Kawaguchi.
[9] In June 2003, Shiina released his second original album Amai Yoru no Kaori, led by the single "Time of Gold", a duet with Ryoko Shinohara used in a Japanese commercial campaign for Canada Dry ginger ale.
[15][16] Shiina is inspired by soul and R&B singers, including Marvin Gaye, Teddy Riley, D'Angelo and Donny Hathaway.