Due to being a southpaw, Oki is chosen to be one of the reserve pitchers of the Nishiura baseball team's lineup. He had more pitching experience than Hanai, but was reluctant to admit it as he does not really want to pitch in official games, and had only done the first baseman position since 3rd year of his junior high.
Oki has short, black hair and hazel eyes. He is more often than not seen wearing the baseball club's, or the school's, uniform.
Similar to Mihashi, Oki is also a nervous boy with little self confidence. During Mihashi's breakdown on Tosei's match, he was afraid to take Mihashi's position as a pitcher because he does not have any confidence to do so. However, he was inspired by Mihashi's dedication and decided to try his best.
He is also afraid of Abe, especially when Abe starts raising up his voice. At one time when Mihashi ran away as Abe's voice started to get intimidating, Oki was the one to mention this to Abe, even though Oki himself feels scared of Abe.
- On the topic about fantasies, he likes girls in traditional japanese clothes and mikos.
- It seems that he is good at calligraphy. (Volume 17 Omake)
- He, Mizutani, and Abe, as of chapter 66, are the exact same height.
- Oki went to a swimming school up till 6th grade and was a two-time breast stroke representative.