Ichimaru Gin prefers to think of himself as an enigma to those around him. He is an extremely complex and complicated character, one so set on revenge and setting right the wrongs that have occurred in Rangiku's past, that he easily loses sight of what is truly important. He is classified as a traitor by Soul Society, along with that of Aizen Sosuke and Tousen Kaname, and he seemingly joins forces with them in Hueco Mundo. We only find out in the midst of the Winter War in Karakura town that Gin's motives were to keep his enemy (Aizen) closer than anyone else, and to kill him with his own two hands. Despite his intentions being pure — to kill the man who stole a piece of Rangiku's spiritual pressure against her will as a mere child—, he dies without a single soul knowing all that he sacrificed. Those he seemingly betrayed are left with nothing to hold onto; no mementos, no answers to the questions they so desperately sought out.
Gin is a sneaky snake when he wants to be, and he is painstakingly good at being one. He slithered his way through the Shinigami Academy, and through rigorous training sessions with the man he loathed more than anything or anyone else. He managed to push out all of his emotions and ties to Soul Society in order to follow through with his goals, ignoring all of his mistakes and the people he had harmed along the way. But deep down, despite his creepy exterior and nerve-wracking demeanor, he is in love with Rangiku, and all of those years ago, despite every bone in his body telling him to run, he chose to fight for what he felt was right, and for the girl he wanted so desperately to protect... even if he was only to be blinded by hatred, and to wear the mask he had so elegantly developed as if it were his own skin.
He only realizes his failure in the end, while Rangiku's tears seep through the paling skin of his cheeks. That he had lost himself along the way, and had become the monster he had longed for nearly all of his life to destroy. It is evident in his volume poem, and in the flashbacks of his childhood. And it is also evident in his unspoken apology.
Ichimaru Gin is a tragic character, one that's true intentions aren't revealed until the very end. Despite all of the turmoil and pain and anger he feels on the inside, and despite the grin that happens to scare others in his presence, he can also be funny and sweet. There are many different sides to this sneaky little snake, just as there are endless possibilities to explore and to learn about, for he is constantly evolving, even in death.