Kekkaishi - Season 1 Episode 20 Weird Surveillant

Yoshimori engages in battle with the spy but the spy runs away. Yoshimori chases after him outside the school grounds but the spy runs into the forest. Yoshimori envelopes a large part of the forest with a kekkai and the spy is trapped, but then he drinks a power-up drink and strengthens himself and rips the kekkai apart. The spy swings his arm in a circle creating a mystery circle and uses the confusion to escape. Yoshimori is left with the spy's right arm as evidence.