- Before the Fall manga
Isaac had light hair cut similar to a bowl cut, with a darker mustache. He wore the typical uniform as a member of the Survey Corps.
While it is not certain but due to being a member of the Survey Corps, it is presumed that Isaac had a sense of bravery and was driven to help mankind succeed against the Titans.
Isaac was among the most recent members enlisted at the Training Academy in Wall Rose. Despite not volunteering to be among the special training class to learn how to use the vertical maneuvering equipment, he was aware of it and was taught the basics by Jorge and Carlo Pikale.
After the training period ended, Isaac was officially made a member of the Survey Corps along with all the other trainees. He showed enough progress and skill to be made one of the expedition's team leaders, along with Simon Barna and fellow trainee Rosa Carlstead.
Given control over team seven, Isaac traveled with Carlo Pikale and most of the expedition teams towards an oasis located ten kilometers beyond the Wall. After a red signal flare is sent, Isaac is ordered to protect the wagons and to regroup with teams nine and ten back at the first oasis marker located five kilometers back. En route, both teams seven and eight encounter an unknown number of Titans, including a ten meter one; due to the poor conditions of the terrain, Isaac and the members of both teams are unable to effectively protect themselves and are swiftly killed. His mangled corpse is soon discovered by Rosa, Simon and the members of both teams nine and ten.