Soutaisei Riron (相対性理論; "Theory of Relativity") is a Tokyo-based Japanese rock band formed in 2006 and signed to Mirai Records. The band is known for not revealing information or taking photos; they do not appear in press or their promotional videos and have very small interaction with the audience during live events. Soutaiseiriron debuted in June 2007 with the mini-album Chiffon Shugi. The album was remastered and re-released in May 2008, and topped Tower Record's indie chart. Following the success of Chiffon Shugi, they released their first studio album, Hi-Fi Shinsho, on January 7, 2009.
Members: Etsuko Yakushimaru (やくしまるえつこ) - Vocals, Illustration and Narration Kyo Yoshida (吉田匡) - Bass (joined 2012. ex. OKAMOTO's) Seiichi Nagai (永井聖一) - Guitar itoken - Drums (joined 2010. also of the group, d.v.d -previously collabing with vocalist, YakuEtsu) Motoki Yamaguchi (山口元輝) - Drums (joined 2012.)
Former members: Kensuke Nishiura (西浦謙助) - Drums (Founding member. ex. Luminous Orange, ex. support Mass of the Fermenting Dregs) Shuichi Manabe (真部脩一) - Bass (Founding member. Producer for Pop singer, Hanae, from her single in 2012 till her album in 2015, and member of the theatrical black metal group, Vampillia)
