Talk:Quests/@comment-121.7.186.115-20151214090442/@comment-5380363-20151215055304

For that quest, you need to reach the Boss node (Big Red Node with horned devil-like shape) and get a victory there. Normally, you shouldn't have much trouble getting S-rank there, though I don't remember if you can clear it without sinking the flagship (the enemy in the highest slot). You should go ahead and try to sink it anyway, just to be on the safe side.