Sei is part of the generation before Rou. She was a hobgoblin mage when first introduced into the story. She later becomes the leader of Agony.
Sei is smart, has high wisdom, and has a cool head among her generation and her younger generation, as can be shown in the first conflict between Rou and Hobuken. She prefers to avoid pointless fighting and tends to not get into ranks of stronger goblins during non-magic competitions. She may go really far to attain her objectives. She has the habit to spend a lot of money to acquire Grimoires.
