Invaders of the Rokujouma!? Volume 43 by Takehaya

Koutarou and the others have at last defeated and captured Ralgwin, the leader of Vandarion’s faction. Given his importance to the rebellion and Fasta’s threats, however, Forthorthe is convinced it’s only a matter of time before his allies stage a jailbreak. They put everything on the line to keep him in custody. Even the court magicians and the princesses are getting involved, which complicates things for Grevanas. The old wizard grows desperate and finally decides to make his move. With neither side willing to back down, a grand battle lies ahead.