Starting the other day MDN:WaiWai has a short series of articles detailing Schoolgirls' Decade of Decadence, covering everything from selling panties to schoolgirls offering sex for a ride or train fair.
Where Eriko and Chiharu differ is that they exchange their filthy favors for things as simple as a lift to work, or for train fare. Spa! says they treat prostitution like an ATM with no limits, like a pot they can dip into whenever the funds run low. [MDN:WaiWai]
As is usually true when reading WaiWai, words fail.
