Sebastian is a massage chair who serves Nail Saionji. In duels, the character utilizes a Chair Deck. This deck contains the monsters Dahut Ahez the Mirror King of Ys' Throne, Dayu the Dark King of Chairs, three copies of Dwell Chair Massage, Dwell Chair Scale, and Throne of Darkness. Sebastian engaged in three documented duels. The character first dueled Yuga Ohdo in episode 19 and was defeated. A subsequent duel against Finger Chikako in episode 34 also ended in a loss. Finally, a duel against Nail Saionji in episode 83 concluded with another defeat.