Issak manga omnibus volume 2 contains volumes 3-4 and features story by Shinji Makari and art by DOUBLE-S.

Issak and Prince Heinrich's gambit to defend Fuchsburg Castle may have worked, but the reprieve is short-lived. Crown Prince Alfonso's mercenary forces, led by an Ambrogio Spinola seemingly back from the dead, have issued an ultimatum to the nearby city of Rosenheim: cut off all resupply to Castle Fuchsburg—dooming it for certain—or be destroyed. Leaving his men to defend Fuchsburg, Prince Heinrich and Issak travel to Rosenheim to lead its small garrison as the city braces for a siege, where Issak is met with a bracing encounter with his past…