Here’s a detailed write-up on the specific episode in Attack on Titan Season 1 where Eren Yeager first transforms into a Titan. (Japanese: 原初的衝動, Genshoteki Shōdō ) Season 1, Episode 9 (Overall Episode 9) Original Air Date: June 2, 2013 Context Leading to the Transformation Prior to Episode 9, the cadet corps—including Eren, Mikasa, Armin, and others—are thrown into the breach of Wall Rose after the Colossal Titan breaks Wall Maria. During the Trost District battle, Eren is tragically swallowed alive by a bearded 15-meter class Titan while attempting to save Armin from being crushed by falling debris.

From Eren’s perspective, he experiences a dark, dreamlike sequence where he sees fragments of his father Grisha’s memories—a key, a basement, and a strange injection. When he wakes, he finds himself not dead, but , surrounded by the bones of previous victims. The Transformation Moment In a fit of rage and desperation, Eren yells, screaming about how he will destroy every last Titan. At that moment, a blinding flash of lightning strikes from a clear sky directly onto the Titan that swallowed him. The blast creates a massive crater in the ground.