Walknal-S

Walknal-S is a product which Run bought via the Galactic Courier.

Features
It looks an ordinary spraying can with a drawing of evil face labelled on the product.

The agent of this spray turns the personality who are sprayed into sadistic, evil or perverted. The effect only lasts for a temporary period.

Plot
Run wanted to use it to Lala in the chapter 140 of To LOVE-Ru, for turning Lala evil thus Rito would hate her. But when she tries to spray it to Lala, the Principal appears asking Run to sign his body and Run accidentally discharges the spray to Haruna turning her into a mean and perverted girl.

The new Haruna goes on a rampage through the school while Rito tries to chase her down. He eventually does and, despite he don't like this version of the girl, is forced to give Haruna a "horse ride" to protect her from Saruyama and the Principal. Meanwhile Lala and Peke found the Walknal-S, lost from Run, and understand its the cause oh Haruna' behavior. The effects wear off after school.

Trivia

 * Its name deriving from "Warukunaru" means "becoming bad" in Japanese.