After rejoining the Kingdom of Science, he is placed on the Power Team and usually helps with building things and farming and gathering.
After his second revival, his scars disappeared and he soon adorned war paint in reflection of his stone markings, during Tsukasa's revival.
Taiju is an outgoing, friendly, and kind person. He's enthusiastic about performing even small tasks and a diligent worker. He is very determined when something is important to him.  He tends to yell loudly and is enthusiastic regardless of the task so long as he proves useful. He is persistent and determined. Despite being emotional and expressive, he has great control of his temper, never losing his cool or acting impulsively. He is notably one of the kindest people in the series, refusing to murder Tsukasa and wanting to find peaceful solutions without murder or hurting others as evidenced by his pacifistic nature. He has a straightforward and honest nature, refusing to take a love potion that Senku claimed would make him irresistible and stated he would confess to Yuzuriha on his own. In addition, he tends to easily trust others and believe in the good of others, believing Tsukasa to be a good person when they first met for wanting to eat the meat of a lion he killed as not doing so would be disrespectful of the lion's death. Even after becoming enemies and witnessing him "murder" Senku, he shows no rage or anger despite greatly mourning his friend's "death," instead wishing Tsukasa a benign farewell.
He loves Yuzuriha, although he couldn't bring himself to confess his feelings for five years. It was his drive to finally tell her how he feels that allowed Taiju to remain conscious during his several thousand-year petrification. Even after they are de petrified, he has yet to confess his feelings because he does not want her to feel pressured to answer how she feels when he believed they were some of the only few humans remaining. He also refused to de-petrify her until after clothing her, proving to be a gentleman and considerate of the feelings of others. He is a loyal friend and person to those he cares for, placing great trust in Senku and being deeply loyal to Yuzuriha.
He greatly admires his best friend Senku, even though he only has a limited understanding of scientific practices. He gets easily impressed by Senku's inventions and he assists Senku with his experiments by providing the manpower necessary for them.
Despite his massive strength, he is a pacifist who refuses to fight others because he does not want to hurt others. He once even offers to let Tsukasa smack him until he is satisfied in the hopes of deterring him from destroying anymore petrified humans. Nonetheless, he has the endurance and patience to complete any task no matter how arduous.
While considered book dumb and not good with science, it is shown that he is capable of finding mundane solutions without science and can apply the science and knowledge Senku imparts on him and use it to his advantage, such as remembering how Senku stated that shells were good for upgrading soil for farming and applying it to his fields, which allowed it to grow in contrast to Yo's and Magma's fields. He can be resourceful and also has a good memory, managing to remember that, in the past, Senku did not have the habit of cracking his neck and figuring out it was a code from Senku. He also knows his limitations and what he is good and not good at without overestimating himself.
Abilities and Skills
Taiju possesses an extremely sturdy body, something his friend Senku vouches for. Besides Senku, he remained awake while petrified because of his strong will. He is the first human to be able to withstand a kick from Tsukasa without immediately losing consciousness. He also possesses immense stamina, able to cross 80 kilometers in 5 hours. Gen Asagiri has also noted that his stamina is immense. He is also the strongest man for endurance after Tsukasa was put in cryosleep and Hyoga was incarcerated. Magma, Ginro, and Yo notably respect Taiju due to his perk of "limitless stamina" that surpasses even the strongest man in Ishigami Village.
- He moves faster and brings with him some loot.
For a high schooler, Taiju is incredibly unintelligent. Taiju is shown to possess below average logic and knowledge, easily on par with the Ishigami Villagers (minus Kaseki and Chrome) in how little scientific knowledge he possesses. For example, at one point, he thought the base component for gunpowder would be fireworks (its the other way around). It is safe to assume Taiju did poorly on tests and was probably held back a few school years back in the Pre-Petrification World.
Chapters This Section is Unfinished, Add on to it
- Taiju's name is composed of "tai" (大 big; large) and "ju" (樹 tree) to create Taiju (Big Tree), while Ōki is composed of "ō" (大 big; large) and "ki" (木 tree) to create Ōki (Big Tree).
- This means that his name is literally "Big Tree Big Tree".
- Taiju shares a motif with Senku and Yuzuriha in that his name contains "ju" (樹 tree) and "ki" (木 tree) in his name, which correlates to the theme of "land, sea, and sky".
|Male||Taiju Oki • Senku Ishigami • Gen Asagiri • Chrome • Kaseki • Kinro • Ginro • Magma • Ryusui Nanami|
|Female||Yuzuriha Ogawa • Ruri • Kohaku • Suika • Nikki • Minami|
|Male||Byakuya Ishigami • Gen Asagiri • Hyoga • Ryusui Nanami • Senku Ishigami • Shamil Volkov • Taiju Oki • Tsukasa Shishio • Ukyo Saionji • Yakov Nikitin • Yo Uei|
|Female||Connie Lee • Darya Nikitina • Homura Momiji • Lillian Weinberg • Nikki Hanada • Yuzuriha Ogawa • Minami Hokutozai • Mirai Shishio|