The cool air across her shoulders was becoming a distraction(when had it gotten so chilly?...), but Ami had to persist. If she put Berthier in check, or better, mate, this could all be over in minutes. She took her knight, and moved forward again. Berthier took a moment, then moved a pawn. Perfect, still no threat.
Ami regarded the board with a quick glance, then moved her knight to the side, finally within range of the rook. Only one more move and she could take it. Ami withdrew her hand, Berthier took up a piece, and moved... a bishop. Right into the path of her knight.
"W, wait a moment, when did-"
Ami saw the pawn that the pale-skinned woman had moved, far too late. It had left her bishop a clear line of attack, and so Ami's knight was taken off the board.
"You need to be more careful, Ami. You are being a little..."
Berthier set a gloved hand beneath her chin, and watched Ami's face turn bright red, and smiled. "...careless."
She did not see the clear result of the knight's capture, but Ami did. The lower half of her ensemble, that of a modest coordinated skirt, had vanished utterly.
"N, no... why is..." Sure enough, Ami's own panties were staring her in the face. Her legs were in plain sight. She had on just her underwear, socks, and shoes.
"G, give that... back!"
Berthier clicked her tongue, and frowned. "Such poor competition, dear. We have to continue until the game is over, I'm afraid. Now, it is your move..."
Ami shivered, staring around in growing horror. No one was watching yet, somehow. Maybe it wasn't too clear. Ami gulped, and stared across the board. Things were getting desperate. Maybe it was better for her to get away while she could.
She could save her friends some other way, it seemed favorable to letting Berthier humiliate her.
Ami knew what had to be done, and so the half-dressed girl...