Seiji is (in my opinion) the most useful of all the Troopers in battle. Seiji also controls the Korin Armor. It is a very powerful armor with extroidinary capabilities that go beyond those of the other armors. Let's take a look at the origin and ability of this magnificient armor and the way of Seiji's fighting.
Seiji was forced by his grandfather into competing in a Kendo tournament against Kazamatsuri Shingo, another famous Kendo practitioner. Shingo had never been in the Junior's tournament against Seiji before and wanted to try. During the fight, while Shingo was losing, he throws something into Seiji's left eye. His right eye was covered by his hair. Seiji gets really pissed and hits him straight in the face knocking his face mask off and knocking Shingo out. This is TOTALLY against etiquette. Seiji's grandfather, furious because he used prohibited skills, sends Seiji to the hanare (a separate building from the main building). Seiji didn't believe what he did was wrong because he felt that if he hadn't done what he had, then Shingo would never have been a true swordsman. Therefore, Seiji showed that he knew the concept of Rei and the Korin Yoroi showed itself. Some time later, Shingo sent a letter to Seiji hoping to see him again at next year's tournament. If anyone is interested, here is what the letter said:
"I regreted hearing your absence at this year's Tournament......But, a tournament without you had no challenge. And even though I won, I don't feel satisfied. I believe that I'll see you there next year ...."
Seiji's green yoroi is Korin, or Halo, and it draws its power from light. In battle, his weapon is a sword. His weapon is called a no-daichi (a big-ass field sword) that must be near six feet long (taller than Seiji) and God knows how much it actually weighs. Seiji swings this huge sword one-handedly, like it weighs nothing at all. Sometimes I wonder how strong Seiji is. I mean, if he controls that sword like its nothing.... Another really strange thing about Seiji's sword, is that the sword also reflects the owner's mental condition. If the owner is confused, or is corrupted by evil, the sword loses its light. The prime example was in the episode, "Shallow Darkness." Seiji lost a lot of the brightness in his sword because he was very confused in all the darkness. Depending on the brightness of the sword, is how focused Korin is.
Now, in the American version, Seiji has the power of wisdom. In the Japanese version, Seiji has the power of Rei, or courtesy.
Seiji likes to have a plan whenever he is in battle. He is usually the first one you hear that says they all need a plan. He doesn't like to rush into battle and he always considers the consequences.
Seiji's main rival is Anubis (Cale). Seiji is the only Trooper with a exact opposite and is one of the few Troopers who could defeat a warlord on his own. Anubis controls the power of darkness corruption. Seiji controls the power of light and when his armor is at its maximum power, he has the strangest ability to heal.