Reiner Braun

Birthday: August 1
Height: 185 cm (6'1")
Weight: 95 kg (210 lbs)
Affiliations: 104th Trainees Squad, Scouting Legion
Graduation Rank: 2nd

Strong willed, with a solid constitution. Most adept at gaining the trust of his comrades. Ranked no 2 of the trainee class. Helps Eren out during his training days.

Major Spoiler

It is later revealed that Reiner is a Titan-Shifter. He is the Armored Titan that opened the gates of Wall Maria along with his partner Bertolt, the Colossal Titan, with the intention of slaughtering the wall's inhabitants.
Note: Reiner Braun is the official English translation by Kodansha.