Saint Seiya: Sanctuary Battle

For Mission Mode Courses, this is only a matter of being quick and scoring a lower time. For that, Readiness, Road to Perdition, and Unbending Heart can be a great help, despite often being hit and killed, but course times are quite generous to begin with. You do need to complete all Offline and Online courses in Single and Tag, but Survival stages do not count towards this, nor do any DLC courses.

For Story Mode, a great number of A ranks should be gotten from your three playthroughs. For any missed A ranks, they can be easily gotten by selecting the stage from Story Mode's stage select, then playing that stage on a low difficulty with a strong character. While high difficulties provide a bonus to your score, low difficulties provide greater opportunities for higher damage dealt, lower damage taken and a faster time, all of which will go a long way to getting an A Rank in Story Mode.