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Two kind hearted characters who dealt with multiple world threatening alien invasions (The Septentriones, and the Triangulum, & The Numbers and The Barians), with methodical companions that only they can see, accompany them on their journeys (Tico and Astral).

They were part of groups formed to help combat these invaders, mostly with their friends (JPs, and the Numbers Club)

They are able to summon powerful monsters using special devices (A COMP and A Duel Disk), and can harness them for supernatural effects (The Skill Crack, and Shining Draw.)

Both have access to legendary powers (The Dragon Stream and The Shining Draw Ability), that are normally wielded by powerful lineages (The Hotsuin Family, and the citizens of Astral World), granted to them by members of said world (Shakko, the Dragon Stream itself, and Astral).

Both were once allies with enigmatic characters who turned out to be members of the alien race they were fighting (Al Saiduq/Miyako Hotsuin as a Septentrion and Triangulum respectively, and Shark, a Barian), who they had to fight and inevitably kill to help defeat an all powerful being that was trying to destroy their worlds (Polais/Canopus, and Don Thousand).

They eventually harnessed the power of a device that is capable of rewriting all of reality, and used it to fix the destroyed world, and resurrect those who previously died (The Akashic Record, and The Numeron Code)."