Clean Leaf

Clean Leaf (キレイなハッパ, Kireina Happa) is a drug from an undisclosed plant used for recreational or therapeutic purposes. Basho is a frequent user of the substance and, very likely, its "inventor".

Overview
Of vegetable origin, the leaf is a drug considered "clean" (healthy) because it is less harmful than other types of narcotic substances, having even the potential to be used therapeutically in the rehabilitation of addicts of other drugs (like heavy smokers). To have, cultivate, or use it one needs a license, since its legal status seems to vary from place to place (from restricted to prohibited). Basho is implicated as being the Clean Leaf's creator.

Succession Contest arc
Four hours after Black Whale's departure, Luzurus and Basho smoke the latter's Clean Leaf together in the Room 1007. Luzurus is surprised that it is legal, to which Basho replies that the recipe can be found on his home page and that the license he owns protects him from being busted. Basho says that, of the various things he has already used, the Clean Leaf is what he always comes back to.

When he states that it works best on heavy smokers (as proved by his friends becoming healthier), Luzurus wonders if it could be used to rehabilitate drug addicts, although Prince Benjamin, who (as the head of the military) is in charge of drug control, would never support it. Luzurus adds that recently a friend of his overdosed and asks Basho how he would feel about publicizing the results of a clinical trial. The Hunter gives his permission, but asks if it would not be quicker if Luzurus just became Kakin king, which prompts the prince to retort that it is not that easy.

Trivia

 * Clean Leaf probably is Hunter × Hunter's counterpart for real-life cannabis (a.k.a. marijuana), was inspired by it, or is a nod to it. Among the notable similarities are:
 * both originating from leaf of plants;
 * both being drugs that one smokes (the most common in cannabis' case), notably in the form of a joint;
 * both having controversial and mixed legal status;
 * both being for recreational and therapeutic/medicinal purposes;
 * and, both needing some kind of license for use/possession/cultivation.