Saint Seiya: Destiny is a oneshot manga which is a sequel to Saint Seiya: Origin which is a twoshot manga prequel to the original story. Thus to understand the context of this story or be invested in what it has to tell one has to watch or read Saint Seiya to begin with. As this is a story for the manga specifically fits only the manga and would make less sense when reading it after watching the anime. Saint Seiya: Origin focused on the backstory of the Gemini Gold Saint twins. From how they were born to how they became the people they were in the main story. Well kinda since there were many time jumps and only a few things were teased also spicing things up with some lore for that fans loved. The problem with that prequel story was it kinda soured the mouth on Sagas split personality. While in the context of Saint Seiya it can be argued that it could make sense the other Gemini Gold Saints that were introduced past Saga kinda conflict with that idea and make him a lesser character in the long run. Meanwhile Kanon got screen time but not much of his character got explored. This is where Saint Seiya: Destiny comes in to flesh him out a bit. We see him interact with the other higher ranked Mariner Generals and explain some things how Isaak became suspicious of Kanon. Saint Seiya: Origin was already lacking in content to fully satisfy people who were expecting something from the Gemini Saints past. The things shown were interesting and did answer what is necessary for the story it left still a lot to be desired. Saint Seiya: Destiny did not even get that much. It introduced more retcons making a character introduced in Saint Seiya: Origin more important and souring some moments in the Hades Chapter. On top of that said character has yet to reappear in any future Saint Seiya continuation thus she exist more as a plot device rather than a character. The Kanon portion of the story is great as it explores more of his plans and mindset. The scene with Isaak while it felt good as Isaacs reason for suspicion is explained. Like with Saint Seiya: Origin the art itself is on par with the quality of the Hades Saga of the manga. All in all Saint Seiya: Destiny is more damaging than satisfying to the story of Saint Seiya. It has its good part. It told what it wanted to tell and added extra content. But said extra content which is the Saga part was the worst part leaving the overall experience with a disappointment. It also made two characters that seemed redeemed appear worse again tho with some headcanon one can argue otherwise. If you feel you can tolerate some retcons and already read Saint Seiya: Origin you might want to read this manga as well or you need to get more Saint Seiya lore. Otherwise I suggest you skip on this one.