He is a recruit of the Scout Regiment. He joined the regiment after the crowning of Historia Reiss.

The battle to retake Wall Maria begins now! With Eren’s new hardening ability, the Scouts are confident they can seal the wall and take back Shiganshina District. If they succeed, Eren can finally unlock the secrets of the basement—and the world. But danger lies in wait as Reiner, Bertholdt, and the Beast Titan have plans of their own. Could this be humanity’s final battle for survival? 
 
(Source: Funimation)

[Wiki (jp)](https://ja.wikipedia.org/wiki/%E4%BD%90%E4%B9%85%E9%96%93%E5%85%83%E8%BC%9D)

In this post-apocalyptic sci-fi story, humanity has been devastated by the bizarre, giant humanoids known as the Titans. Little is known about where they came from or why they are bent on consuming mankind. Seemingly unintelligent, they have roamed the world for years, killing everyone they see. For the past century, what's left of man has hidden in a giant, three-walled city. People believe their 50-meter-high walls will protect them from the Titans, but the sudden appearance of an immense Titan is about to change everything.
 
(Source: Kodansha USA)
 
Note: Includes 2 extra chapters.

Eren and his companions in the 104th are assigned to the newly-formed Levi Squad, whose assignment is to keep Eren and Historia safe given Eren's newly-discovered power and Historia's knowledge and pedigree. Levi and Erwin have good reason to be concerned, because the priest of the Church that Hanji had hidden away was found tortured to death, making it clear that the Military Police are involved with the cover-up. Things get more harrowing when the MPs make a move on Erwin and the Levi Squad narrowly avoids capture. Eren is also having problems with his Titan transformation, and a deadly killer has been hired to secure Eren and Historia, one Levi knows all too well from his youth. 
 
(Source: Anime News Network)

Gordon