I guess this just goes to show that anything can be ecchi if you're determined enough to make it ecchi. Just have the panels always focus on the boobs and butt, and make the girls' shirts unnaturally hug their underboob and their skirts hug their crotchline, to get the full curves of nudity even when they're clothed. Then have your characters get sexual pleasure from drinking water, using chopsticks, opening doors, and other everyday activities--under the guise of learning the simple pleasure of breaching etiquette. When that inevitably isn't risque enough, introduce a friend who can end each chapter with an orgasmic groping session. And turn the series into a sexual version of Dumb and Dumber, with the two main characters coming to retarded levels of misunderstandings.
[Reviewed at chapter 18]