Eren and Reiner's Reunion

Attack on Titan is about a civilization that lives within gigantic walls that protect the citizens from giant man-eating mindless beings called titans. Its main protagonist is a boy named Eren Yeager who watched his mother get eaten by one of these titans after their home was attacked. This attack was plotted and caused by two powerful and sentient titans who created a breach in the wall that allowed the mindless titans to flood inside the walls. After witnessing his mother get eaten, Eren swore vengeance on all titans and joined the Survey Corps, a branch of the military that explores the outside of the walls where the titans reside in order to learn about them. Among the other new trainees was a slightly older boy named Reiner Braun. Reiner fit the stereotype of the "perfect soldier". He was strong-willed, strong bodied, smart, and took the role as a leader among the trainees. He often encouraged Eren to keep going whenever he stumbled, and Eren looked up to Reiner almost as an older brother. However, it turned out that Reiner along with his two friends that he joined the Survey Corps with were the ones who were behind the breach of the walls that led to the death of Eren's mother. Later in the series, the story shifts and centers around the antagonists side. Here, we learn that Reiner is also a victim of his own circumstances. Basically, he comes from another country outside of the walls called Marley that plotted to destroy all of the inhabitants within the walls (the Eldians). Reiner happens to be a descendant of the Eldians born in Marley and as a result, lives in harsh conditions and is treated as a war prisoner along with others like himself. In order to become a honorary Marleyan and create a better life for himself and his mother, he became a warrior and was given the powers of the Armored Titan and sent with a few other children to destroy the Eldians within the walls. Despite initially only pretending to be Eren's friend, Reiner actually grew to value Eren and the other trainees in the Survey Corps as comrades. As a result, it has been shown that Reiner's sanity has been steadily deteriorating because of all his pent up guilt. At the ending of the most recent issue, Eren infiltrates Marley and finally comes face to face again with his worst enemy. His reaction seems a lot more calm then what most would have expected. What do you think will happen?