Since we're having a rare Japan-U.S.A. joint sleepover, let's have a makura fight! マクラ = pillow

As expected of Akagi-san

Oh, what's a makura fight? マクラナゲ (枕投げ) = pillow fight, although it's more accurately described as pillow throwing.

It's when...

...you do it like this!!

A preemptive strike.