A rather short, old man, probably around his 70's or 80's maybe even 90's. He wears round lensed glasses and is bald except for a ring of grey hair around the base of his head and his chin. He wears a grey or green shirt and shorts along with sandles.
He is old yet is very agile and is extraordinarily great at fighting and pool. As evidence of the mask over the elevator, he presumably went to the void and his soul lost when he was the one to play the game and wasn't the one to cause harm, it would most likely have to do with his past of being a delinquent. Also right before the elevator doors close on him, he gives a very creepy toothless grin and open eyes which he had only opened during the game and when he remembered his life, most likely signifying he had more secrets that we didn't see in his flashback.
This man was the first sub-character shown in the Death Parade pilot episode, and later on again in Sachiko Uemura's flashbacks, giving proof to the theory that they are a couple. He lived a fairly well life, until becoming old, where, due to either a medical condition or age, he became a "vegetable" and could hardly do anything. When he is playing the game, Death Pool, we see that he is cunning and skilled in the game. In the end, he went to the void, with a smirk as doors closing.
For unknown reasons, as evidenced by the plaques above the elevators at the end, after he whispered something to Decim, he was seemingly cast into the void, while the younger man was reincarnated, despite the younger man acting violent and hostile as he began to lose the game. There are couple of theories which speculate why:
1. Exchanging for Request (Very likely)
It is possible that the Old Man was supposed to go to the reincarnation but decided to request Decim to swapped it instead. Mostly because he thinks the Man deserves a second chance despite cheating on his girlfriend and end up being murdered by her, or it could be hinted at a supposedly future (Get married and have a family).
2. Colors of the doors (Very unlikely)
As depicted of the elevator doors appearance, the left door represents Reincarnation as the white mask represents it and the right door represents Void as the red mask represents it. This was proven false as it was shown in episode 3 of Death Parade, Miura and Mai went to reincarnation instead of one goes to the void.