He was a tall man with rust-red eyes and reddish-brown hair which was slightly parted so that a small area of his forehead was visible. He also had light stubble similar to Mori's.
His attire consisted of a black-and-white pinstriped collared shirt which he wore loosely, as the collar covers part of a long-sleeved beige brown coat with brown buttons on the cuffs. His pants were pale grey, whilst his shoes were light brown.
Oda was a man described as kind, despite working for the mafia, by Dazai. He had a nice temper, and so, was one of the few persons in the mafia who seldom killed. Nevertheless, when furious, he showed amazing and strong fighting skills that Dazai had warned Akutagawa about. Dazai called him "a man who has no ulterior motive". Oda means what he says, and sometimes mistakenly assumes that about other people—for example, when he gave serious responses to Dazai's joke explanations of how he got his various injuries.
However, he also had an incredibly perceptive side to him that allowed him to come the closest to understanding Dazai, whom he referred to as "his dear friend, who had grown tired of the world and is simply waiting to die." It is his understanding of Dazai's loneliness, as well as his regret of not being able to do anything about it, that prompted him to leave behind the last words that became the trigger for Dazai deserting the mafia in favor of carving a brighter path for himself, something that Oda wanted to do.
Oda's ability, Flawless (天衣無縫, Ten'imuhō?) allows Oda to predict 5-6 seconds into the future. It is an extremely powerful ability that renders most surprise attacks useless, as Oda can see them coming 5 seconds before. However, it has its limitations. Since Oda can only see 5-6 seconds ahead, if the time between triggering a trap and Oda realizing that he's in danger is longer than 5-6 seconds, then Oda wouldn't be able to use his ability to save himself and 'un-trigger' the trap.
The future that Oda sees with this ability is also limited to his current decision. If he decides to change his actions based on the vision he sees, then he'll see another future play out - one that might reveal another danger that he wasn't able to see before, and it may be too late to avoid it at that point.
Oda used to be a freelance hit man, doing contract assassinations and was ruthless in his line of work. However, his meeting with a middle-aged man in a cafe changed him. The middle-aged man caught Oda reading the first two volumes (out of three) of a novel he salvaged from one of his recent victims' houses, and commented that the last volume is an atrocious piece of work and Oda should be happy that he only has the first two volumes. The man encouraged Oda to write his conclusion to the novel, and later gave Oda the last volume of the series but with the final pages missing.
"To write novels is to write about humans"—Oda took the man's words to heart, and, believing that a murderer has no right to write about human lives, decided to never kill again in hopes of becoming a novelist eventually and writing his conclusion to the book in a room with an ocean view. He also strived to be a better person in general (a piece of advice that he would later give to Dazai Osamu), adopting five children that were orphaned as a result of particularly intense conflict between underworld organizations. He became somewhat of an oddball in the mafia, known as 'the mafia member who doesn't kill'.
After the Dragon's Head Conflict, he took in 5 children, four boys, and one girl: Kousuke, Katsumi, Yuu, Shinji and Sakura, children who were orphaned after the incident. He mostly leaves them in the care of a curry shop owner. He visits often and the children are fond of him. He leaves money to the shop owner to support the children.
- (To Gide)"The reason why I can't grant your wish is that I have a dream. When I quit the Mafia and am able to do anything I want, I will sit at a desk in a room with the view of the ocean." 
- (To Gide)"I want to be a novelist. I want to throw away my gun. All I want in my hands are a pen and a paper. A certain man once told me that writing novels is writing people. You cannot write about someone's life after you rob them of it. That's why I will never kill again." 
- (To Gide)"I wanted to be a novelist. Someonce once told me I should." 
- (To Gide)"I have one regret. I never got to say goodbye to my friend. He was always there for me as 'just a friend'. He was bored of this world and always waited for death to come to him." 
- (To Dazai) "Listen. You told me if you put yourself in a world of violence and bloodshed, you might be ale to find a reson to live. You won't find it. You should know that. Whether you're on the side that takes lives or the side that saves them, nothing beyond your own expectations will happen. Nothing in this world can fill the hole that is your loneliness. you will wander the darkness for eternity." 
- (To Dazai) "Be on the side that saves people. If both sides are the same, then choose to become a good person. Save the weak, protect the orphaned. You might not see a great difference between right and wrong, but... saving others is something just a bit wonderful." 
- "People live to save themselves. It's something they realize right before they die, huh...? He was... right..." 
- If Odasaku was still alive, he would have been 27 years old.
- In real life, he is often grouped with Osamu Dazai and Ango Sakaguchi as the Buraiha or Decadent School.
- Furthermore, in the series, this often alludes because the three used to meet in a certain bar, as seen in Osamu Dazai and the Dark Era and illustrated on the calendar.
- He appeared as an event character for the Dark Era collaboration with the game 18 (Eighteen) and Love Heaven.
- He also made an appearance in Kanaineco's Bungou Stray Dogs Wan! for the special chapter Dark Era and a bonus of one of the Young Ace's series.
- It is very likely that's the book he was reading was Kokoro. This is because it is split into three parts, and it was written by Natsume Souseki like the book Odasaku was reading.
- According to the second official guidebook: 
- He thinks he has no particular strength and when it comes to weaknesses, compared to his friends he has no talent.
- His ideal type is a quick-witted women.
- His favorite food is curry.
- In reality, Sakunosuke likes curry so much he wrote an article about it. An autographed photograph of Oda hangs in the Osaka restaurant Jiyūken (自由軒). Jiyuuken happens to be the name of the curry rice Oda favors; it is spicy curry rice with a raw egg on top of it (as what the anime showed).
- He dislikes dishes served during stiff dinner parties.
- He wants to go to a bookstore with his novels arranged there.
- According to the DEAD APPLE official guidebook: 
- He recently finds it fun going for drinks with Port Mafia’s accountant.
- He's been recently worried about the increase in orphans due to the Dragon’s Head Conflict.
- His motto is "Limit to one curry meal per day."