Yay, finally got time for this. ^^ Hopefully these facts will introduce Ren's character better.
1) Ren is a very gentle and sweet guy.
2) He hated the person he used to be, someone incapable of love and understanding of this world, someone who wasn’t able to control his emotion and action, a complete freak.
3) He killed people before because of his horrific past, and for that Saga initially didn’t want him to be part of the group, but Levi insisted until Saga finally gave in as he opened his heart to Ren’s circumstance.
4) There are only two people Ren truly opens his heart to: Levi and his lover named Yuki who died under his own hands.
5) He often acts like he’s careless, but deep down, he cares a lot about the people around him and would share everything he has with them.
6) Although he’s serious most of the time, he starts getting awkward and silly every time Levi is around.
7) He is hopelessly romantic, and his world was turned upside down when Yuki died. But he believed that one day, something out of this world will happen and they will meet again at that place Yuki promised him.
8) He is quite popular with the ladies because of the mysterious aura he gives off and his gentle manner, but he’s actually very shy and doesn’t have any romantic experiences beyond that with Yuki.
9) Yuki and Ren never even kissed, but if that happened, Ren would start getting flustered, embarrassed yet happy and confused, he’s very innocent when it comes to this stuff (sad) =.=”
10) Ren used to blame everything on fate, but now be wanted to take things into his own hands, fighting his way out of his past.