I’ve done this thread for How do you recognize art by Mitsuhiro Arita? but we can keep this going as a miniseries
What elements in Saitou’s artwork help you identify his style?
For instance, when I see a pack being opened I basically know what cards are illustrated by him before even looking. The question is, what features of the art makes it his?
The round pikachu face has been my unreliable giveaway.
When preparing for the Baltimore event @vyzhr and I went back and forth about a dozen times trying to decide if a post card was his art or not 
Some of the elements I recognize in Saitou art are a very vibrant and consistent use of color, and a somewhat anime-style drawing of faces and eyes.
The color in Saitou illustrations is always clear and crisp, and well-suited to the Pokemon. There aren’t artistic liberties taken with the colors. If you think of the standard art of the Pokemon, chances are the illustration (with few exceptions) will look the same color-wise.
Similar to what @thundermoo mentioned, the circular Pikachu face is mirrored in a lot of other cards, where the face is rounded a bit or given more of an anime-style look. Little things like larger eyes, reflections in the eyes, mouth shaping, etc all kind of combine to give it that feel. Saitou’s artwork feels a lot “softer” than artists like Arita even when drawing menacing Pokemon.
Overall, to me Saitou art looks like it could be an anime cel. It’s hard to drill down more on specifics than that, but it’s the feeling I get from it!
For me it’s the thin lineart, the softer airbrushed looking colors/shading, the fairly simple environmental backgrounds and more anime-like style for Pokémons faces. Can usually recognize a Saitou without looking at the illus. Credit in the bottom left of a card, which speaks well to his recognizable style.
