Headrest stay and retaining structure

A headrest stay configured to be inserted from an upper side into a headrest support and to be mounted thereat, the headrest support being formed as a tube, and a lock portion being provided at the headrest support, the lock portion being configured to project from and retract into an inner peripheral face of the tube while being urged toward an inner side of the tube, the headrest stay comprising:

• a detachment prevention slot portion formed in a rod-shaped leg portion that is inserted into the headrest support, the detachment prevention slot portion being recessed toward a center side of the leg portion, the lock portion being configured to enter into the detachment prevention slot portion, and the detachment prevention slot portion including:
• a first flat face portion that is a flat face along a direction orthogonal to an axial direction of the leg portion and that faces a lower side;
• and
• a second flat face portion that is a flat face along another direction orthogonal to the axial direction of the leg portion and that faces an upper side, the second flat face portion including:
• an opposing portion that opposes the first flat face portion;
• and
• a region that, in a vertical sectional diagram cut along the axial direction of the leg portion, is disposed at an outer peripheral side of the leg portion relative to the first flat face portion;
• and
• an upper side angled face portion formed at the leg portion, wherein the upper side angled face portion is:
• provided adjacent to the upper side of the detachment prevention slot portion;
• angled, from an upper end to the lower side, toward the center side of the leg portion;
• and
• connected to an edge at an outer peripheral side of the first flat face portion,
• wherein a virtual straight line that extends toward the upper side in parallel with the axial direction of the leg portion from an edge at an outer peripheral side of the second flat face portion, intersects with a region of the upper side angled face portion other than an upper edge thereof.