Plug and buckle

A plug insertable into and detachable from a socket, the plug and the socket constituting a buckle, the plug comprising:

• a plug base;
• and
• a pair of legs connected to the plug base at respective positions mutually spaced apart in a width direction of the plug, wherein
• each one of the pair of legs comprises:
• a first extension extending from the plug base in an insertion direction of the plug;
• a second extension extending from the first extension in an inward width direction of the plug;
• an engagement portion provided on the first extension or the second extension and being engageable with a to-be-engaged portion of the socket in a detachment direction of the plug;
• and
• an operation portion provided on the second extension, and
• when a force in the detachment direction is applied on both of the operation portions, the first extensions are mutually independently elastically deformed in the width direction of the plug in such a manner that positions of the engagement portions shift from engagement positions to disengagement positions with respect to the to-be-engaged portions.