Ailee and f(x)'s Amber display their close friendship

f(x)'s Amber and Ailee displayed their close friendship through photos on Twitter.

The 'sleeping photo battle' started when Ailee won 'Music Bank' and Ambertweeted, "As expected of our goldfish @itzailee! Congrats on #1~~ 'Rest up'!". She tweeted the above photo of Ailee passed out on the couch.

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In retaliation, Ailee tweeted, "Thanks for the 1st place! In return.... @llama_ajol REVENGE!!!!!", adding on the above photo of Amber sleeping.

Amber has yet to respond, but do you think we'll see this battle continuing on?