Epsilon (stylized as εpsilon) is Blood Stain Child's fifth studio album and first release on Coroner Records/Pony Canyon. It's also the first and only album to feature vocalist Sophia and drummer Gami (after the departure of vocalist Sadew and drummer/founding-member Violator). All compositions—except "Electricity," which is composed by Aki—are by Ryu, while lyrics are co-written by Sophia.^[1] This album was pre-sold during A-Kon from June 10 to 12, 2011.^[2] And, in this event, nine of the new songs (including the European bonus track, "Royal Sky") were performed.^[3] As of June 7, 2011, Pony Canyon released forty-four second samples of each song in the album;^[1] a full sample of "Sirius VI" debuted, through Internet radio, on May 26, 2011.^[4]

Blood Stain Child

• Sophia – clean vocals
• Ryo – unclean vocals, bass guitar
• Ryu – lead guitar
• G.S.R. – rhythm guitar
• Aki – synthesizers, keyboards, programming, backing vocals
• Gami – drums, percussion

Guests

• Claudio Ravinale – screams on "Forever Free" and "S.O.P.H.I.A"
• Ettore Rigotti – vocals on "Forever Free" and "Moon Light Wave",^[5] electronic percussion on "Forever Free".

Production

• Produced/Recorded by Blood Stain Child.
• Mixed/Mastered by Ettore Rigotti.
• Illustrated by Mario Wibisono^[6]