They visited a pachinko parlor.
And they were tasked with completing the mission instead of enjoying the pachinko enough;they had to get over 20,000s point totally(in the pachinko) and if they failed to do they all must be spanked by this parlor attendant.
In the last,they got spanked with the Big Hand for Mission Accomplished.
The spankees are SATO Ami and Mio(,and some guy lol) and a spanker is Momo-chan.
cf. https://www.youtube.com/watch?v=h5oPfPJG1e8