It's ironic and strange now, Atem's arc being about self-discovery and go to afterlife...while the death the storyteller who wrote and draw his character passed away this month, also went to afterlife...
I started with Yugi to celebrate Takahashi Sensei's characters on their birthdays, Yugi was in 4th June, today is Atem according to Gospel of Truth in Ancient Egypt calendar as well, 26th July is Pharaoh Atem's birthday.
The introduction of Atem (AKA Yami Yugi, Dark Yugi, the other yugi) is quite distinctive, he started as his identity was "reset" from the moment the millennium puzzle was completed, he forgotten all his memories from the time he was alive as when he was in his tomb when saved Sugoroku, therefore becoming more susceptible to the "evil intelligence"/"dark intelligence" influence, since he was first introduced as this "mysterious and sinister" Yugi other self, to later as we go along the story bit by bit suspecting something, possibly most of us knew or suspected he was a deceased pharaoh...as it was eventually confirmed in Battle City.
It was always very clear that Atem wasn't "other yugi", it was always heavily implied that he was spirit of pharaoh that died thousands of years ago...
There is discussion if "Dark Yugi" was an evil character in the beginning, was it though? Even after he lost his memories, being more vulnerable to "evil intelligence"/"dark intelligence", he still retained his sense of justice, punish those who harm his host, friends and the defenseless, acted as a guardian spirit, whoever doesn't change the nature of the power of the millennium puzzle being a millennium item that used shadow games and penalty games, it was always from a dark source...other wielders did it, even one who did hardly used was still tempted (yes, Ishizu), even though "Dark Yugi"'s penalty games and shadow games were mostly soft in comparison to others who were much worse, even for punishment - such Shadi and Pegasus.
The only time when you could say "Dark Yugi" kind of killed someone, it's the criminal fugitive with a gun pointed at him, it was legitimate defense and more of the criminal own doing who could take out the gun and pick up the lighter...it was an accident and it wasn't, if it wasn't, it was legitimate defense.
Now that his "main introduction" is out of the way, his character development, some elements of his personal growth are easily overlooked by most people, he was introduced as sinister to becoming less sinister for spending time protecting Yugi and his friends, then the "evil intelligence" influence become weaker, like someone with no memories lost in the darkness and Yugi and his friends was that light that guided him and banished the darkness that surrounded him...bit by bit, going through self-discovery to becoming his loving and caring true self.
Personality wise, he was always the most mature of the gang, he was also quite wise and confident (maybe too much ;), protective, caring, considerate, mostly a softie, strong sense of justice ), however he could be quite cheeky, arrogant and very prideful, a little too "self-righteous" sometimes, and way too considerate to a person's feelings that he cares about if it somehow was damaging for him (he hold back a lot when wanting to know who he was for Yugi), he has his strengths which are mostly "heroic virtues" and some of his flaws (common to see in "hero characters" xD), his personal growth is about to become less overconfident into having a more solid confidence that is stable and learn the importance of humility, overcoming his fear of losing and how pride ends up being more damaging, he learns from his mistakes, from ruthless to becoming more of selfless protective and caring nature that was always inside him...
In Atem's character arc, which was more or less self-discovery jouney in identity and entity, to finish unfinished business about himself and his past, learns parts of himself that he even in personality that he didn't knew, to find his own peace and thread his path to afterlife since he is a soul of someone who died long time ago.
This scene is still my favourite scene of all time, the growth on both these characters shows right here...You can tell how grateful he is that he met Yugi who taught the power of kindness, how much it can extents even making difficult decisions such as this one, so Atem wouldn't spend eternity inside the millennium item for the rest of his existence, while the others would live and go to afterlife, Atem would be the one truly be left behind, which is worse and Yugi sending Atem to afterlife was kindest and courageous thing he did, guaranteeing him that Yugi was not ever weak.
I have coming to notice that Atem didn't cry, also we didn't ever seen him cry, he always tried to keep a brave face like Mai, but this time is so that he wouldn't hesitate as well deep down, very deep down since Yugi completed the puzzle, he always suspected he is a spirit of someone who died and that one day this day would come eventually, discovering his identity further confirmed him that one day he would have to go to afterlife, he is very grateful for the special friend and friends he made along the way to this point.
Even in Afterlife, Atem still watches over them...in times of need, he tries to give a helping hand when he can...
Thank You, Kazuki Takahashi for sharing these characters's journeys, thank you so much...!
Rest In Peace!