Sebastian serves as both a massage chair drone and butler for Nail Saionji, actively assisting his master in suppressing Rush Dueling activities with a focus on opposing Yuga Ohdo and his associates. He utilizes a specialized Chair Deck built around throne and furniture-themed monsters. Key cards in his strategy include "Dahut Ahez the Mirror King of Ys' Throne," "Dayu the Dark King of Chairs," "Dwell Chair Massage," "Dwell Chair Scale," "Throne of Darkness," "Scarechair Gear," "Scarechair Bone," and "Scarechair Saber." His tactics center on monsters possessing 0 ATK, employing trap cards such as "Collapsing Chairs" to destroy multiple monsters under specific conditions and manipulating graveyard counts to summon powerful entities like "Dahut, Dark Rule of the Chair."

Sebastian dueled Yuga Ohdo in episode 19, summoning "Throne of Darkness" and leveraging its effect to special summon "Dahut" after accumulating eight or more monsters with 0 ATK in his graveyard. He temporarily boosted Dahut's ATK to 4000 using its effect, though Yuga ultimately secured victory. Sebastian later faced defeats against Finger Chikako in episode 34 and against his own master, Nail Saionji, in episode 83. Inspired by Rino Nanahoshi's attempt to restore Gavin Sogetsu's memories through dueling during a storyline involving widespread memory loss, Sebastian demonstrated unexpected autonomy by initiating this challenge against Nail. Sebastian appears exclusively within the Yu-Gi-Oh! Sevens anime series.