Colette, who once harbored dreams of becoming a knight, finds herself ousted from the Kiels household after besting her brother in a childhood sword duel. Treated as little more than a servant by her own sister and ensnared in familial intrigue, she is ultimately cast out. Accompanied by Lenri, the loyal butler who chooses to follow her, Colette settles in a small neighboring town. However, fate intervenes, and they find themselves compelled to work at the estate of Duke Rashle, the vice-commander of the Knights, after a series of events. Here, Colette encounters the enigmatic knight, Melchior Rashle, renowned as the Iron Mask. As she uncovers unexpected facets of his persona, Colette finds her heart drawn ever closer to him.