Was early UY one of the horniest anime shows of its era? The show actually tones down the sexuality, and Ataru's lust becomes more about the chase than more explicity sexuality. In fact, nudity seemed to mostly sidelined in the main show, and reserved only for OVA and films from there on out. Could it have something to do with the show losing popularity over time?

Sakura is especially a source of sexualization and an object of lust by Ataru, while Lum and Shinobu are presented in a chaste manner.

While not an ecchi series, it seems to have laid the foundations for them.