Ueki no Housoku

Synopsis

The episode starts off with Kosuke Ueki cleaning up the park. His classmate, Ai Mori, is suspicious that Ueki is an alien. When a tough gang threatens Ueki, he takes a broken part of his broom and turns it into a tree this confirms Mori's suspicions. Ueki has the ability to change trash into trees, a gift bestowed upon him by his teacher, Kobayashi. Kobayashi, nicknamed Mr. K (Kobasen in the Japanese version), is part of a grand tournament to decide the next God, but before Ueki can officially be declared Mr. K's fighter, the middle school student must first demonstrate his own sense of justice. Mr. K is a Celestial King from heaven, or God's helper. The person who receives the power is called a 'Power User'. Also, each time Ueki uses his powers against a non-power user, he will lose an ability (or a Zai in the Japanese version).

(Source: Wikipedia)