Well let's look at it this way: Satoshi is:
A dragon, with all the inanely powerful magic circuits and fire breath that implies**
The owner of a reality marble*
The product of three of the stronkest wizards getting together to protect spacetime**
The true owner of avalon*
Unaging
two thousand years old
A pseudo-lich with his phylactery stand-in in Avalon, making him completely immortal as no one can get there
The owner of a kamen rider transformation device*
A dimension hopper/time traveler*
incapable of running out of prana because of being hooked up to avalon*
an abhorrently strong magus with spells rivaling a highly capable magus in an age where magecraft was stronger than it is nowadays**
A master of dozens of martial arts
Immune to the elements*
Immune to sneak attacks*
Blessed with divine protection
Capable of Resurrection, in the nasuverse of all places**
The owner of Clarent, Mordred's sword*
The owner of a really edgy madness inducing blade*
The owner of a fire-blocking whip***
Somehow not a killer despite going through a berserker phase*
Forget dubious or questionable character creation, this is outright bad. If you can spread your character's traits around and get at least eight characters that are broken/overpowered in their own way, you know something's wrong. That something being: The original character that every single one of those OP traits came from.
He's not a character, he's a brainstorming sheet filled with possible abilities and gimmicks, until you just stopped wanting to brainstorm what to put in and you just threw it all into a story. And being a sheet, it has the personality and intellect of paper.
And yes, I can make that last statement accurately: I haven't read your story nor will I ever, but if you're roleplaying him correctly, he's a bland, personality-less character with the consistency of a schizophrenic mental patient and the intelligence of the chair you're sitting on.
And I know Mike's about to jump in and go "Wait, but by whose standards are you saying he's bad by hmmmm? Who says how you're supposed to make characters and how far you can go making them? And if people do try to restrict that kind of shit fuck them, and the police for good measure." to which I'll reply "Yeah, sure, if you're making characters. Satoshi's not a character, he's a walking, varied exhibition stand with a bland, robotic voice shared by every other character this guy writes except for Connor, because he has a bad cold."
So no, he's not a mary sue. He's not a character either. He's a process you never finished doing before throwing it out in the open.
So go back to brainstorming and finish that process before showing off the result.
And about the whole don't like don't read, here's a treasure: I don't like it and I won't read it, but it's RPing with us so no matter how cancerous the brainstorm is and how much I want to avoid him like the plague, he's still there if I want to be in Cross Effects. Him, and all the other characters from the "Same-voice bland alternate universe" he comes from.
And now you know how I feel.
*What
**This makes no sense
***Whips are about the worst thing for defending, why would you do this