This scenario isn't too difficult, but it can be quite slow. Gaiel disappears as soon as the battle starts, having taken Alhazard and Langrisser (the two swords) away from Jessica, but he's left plenty of very tough creatures around. They'll all immediately begin an attack.

The killer tiger begins by attacking Jessica, but she should be able to hold her own for a while. The Goos are tough against everything, except for Holy troops, so someone with Holy troops would be good to start at the top. It would be wise to take someone across the ship as well, although the Golem and the Scylla will attack you through there. They're not too tough, though.

Try to move as quickly as possible, and hope that none of the civilian generals die. Claret will attack some for you, and give you a big helping hand, but you'll most likely need to help Jessica out. Oh, and don't forget the Devil Axe near the top.