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.

[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.