In this episode,Eri is spanked by Chinpui with a carpet beater and we can watch this spanking on pandora.tv,here (around 11:45).
In short,WAKENAI who is one of old friends of Chinpui came to Earth and he changed Eri and Eri's friends into a Mahl-like alien with his special ability(named "kahou" ,their native Wizardry?) and then caused trouble with them.
So,Chinpui gets angry with them and punishes Eri and WAKENAI together by "Kahou oshiri pen pen".
I wish Chinpui spanked 3 girls and WAKENAI...