Tadokoro has straight, short black hair and small, sharp brown eyes. He is heavily built and is the tallest member of team Sohoku; tying with Midousuji as the tallest overall of the characters in the series' first year. He brags that his large size is due to his abnormally large lungs as well as his bones and muscles. His eyebrows are often sharply downward, though he is not always angry. This sullen look combined with his impressive size can be intimidating.
Tadokoro had an awkward, uncertain, and disheartened personality when he was younger due to his lack of performance during cycling races. He cycled at least since middle school, but did not do well with climbing, came in last at his First-Year Welcome Race and during that year's Training Camp, had to drop out on the second day. He also tried lightening himself by dieting, but found out that deprived his large body of the energy he needed. Unable to find a way to be a winner, he became heartbroken and tried to hand in his club resignation. However, captain Kanzaki Tooji convinced him to focus on sprinting, which he was good at, and then to worry about other skills later, and personally trained him with Coach Pierre's assistance. Having found his path to success, Tadokoro became a member of the Inter High team as a second-year.
Now a successful sprinter, Tadokoro is a loud, confident person with a personality as big as his stature and appetite. He is proud of his abilities and has no qualms about boasting when he wins, and won't allow even a fellow teammate to best him in sprinting or anything else he feels a rivalry about. He will argue constantly with Naruko over the title of the strongest and fastest. He has a tendency to showboat, riling up spectators and openly challenging his opponents to take him on. Though he seems imposing and boisterous, Tadokoro also gets flustered in certain situations, such as when convinced him to sing Love Hime's opening theme song (which he later embraced); and when he encountered some cosplay maids in Akihabara, unaware of how to interact with them.
Tadokoro has a softer side, easily crying tears of sorrow for the defeated underclassmen he trained and when his team's only ace suffered a severe injury at his previous Inter High. He often takes something of a caretaker role among the younger members of the club, taking Aoyagi and Teshima under his wing during their first year and reminding the underclassmen to eat properly during the Training Camp (or in Onoda's case, forcibly attempting to give him a "proper" meal).
In spite of him often stressing the importance of cyclists taking care of their bodies, Tadokoro occasionally displays a recklessness for his own well-being, most notably when he attempts to ride in the second day of the Inter High despite falling ill the day before. Being such a prideful person, Tadokoro seems to dislike or even fear displaying weakness in front of others, asking Makishima to not tell anyone about him falling ill and attempting to laugh off his late start on the 2nd day of the Inter High as giving his opponents a 'handicap'. He often tries to cover any worry or apprehension he feels with a false bravado.
Tadokoro has a competitive streak dating back to his first year, where he loudly declared that he would best Kinjou and the rest of their fellow first years at cycling. He and Naruko are notably competitive with each other, their similar personalities causing them to butt heads frequently. Tadokoro is often aggressive and even rude towards opponents, not afraid of boasting about the strength of him and his team. If someone requests to speak civilly as Izumida Touichirou did after the Inter High's First Stage Sprinters Checkpoint however, Tadokoro is more than willing to reciprocate in like manner.
Despite his gruff and brash nature, he displays a deep kindness and affection for his teammates, both in his actions (such as giving a water bottle to Naruko when he dropped both of his) and words (such as thanking Sugimoto and the rest of the support team for their help during the Inter High). As one of the three senior members of the team, he has a deep bond with Makishima and Kinjou. He is notably one of the most physically affectionate characters in the series, often clapping his teammates on the back or embracing them.
Protective of his team and easily offended, Tadokoro's temper can still cause long-standing grudges (and fists to fly) when he feels his anger is justified, though he can forgive.
Skills and Techniques
Tadokoro is known as the Human Bullet Train & the Rampaging Human Cannonball. Because of his large body, he can wind-block to pull the team, even on climbing sections (Day 2 of Inter High), since he used to attempt to be a climber before being converted. His "Muscle Sprint" is truly strong.
Furthermore, his lung capacity is much greater than that of an average person (8500 cubic centimeters, compared to 4000-5000 cubic centimeters), and he uses this ability as part of his cycling style. By breathing deeply, he's able to feed his muscles large quantites of oxygen, which allow them to produce less lactic acid, and drastically reduce fatigue. During the first day of the inter-high, he showcases this by swelling his chest with air and accelerating rapidly; this technique is known as the "Mach Speed Oxygen Human Bullet".
During 42nd Inter-High, Tadokoro and Kinjou waited over 6 hours for Makishima as his flight from London was delayed. Tadokoro is an aggressively fast driver.
- Honey on white rice, with lots of crunchy tempura bits dipped in dashi soy sauce sprinkled on top. (Hasn't told anyone.)
- Assortment of Seafood and Meat Rice Balls
- Sengoku commanders; he plays the only video game that has Sengoku commanders in it. Since he hates to lose and can't stop playing once he's started it, he is currently keeping himself from playing it.
- Kendama (it was a fad when he was in elementary school, and since he hates to lose, he kept practicing it)
- Speed eating
- Best subject
- Japanese history
- Tadokoro uses a Specialized S-Works Prevail helmet.
- He prefers VHS tapes over DVDs.
- Screams 'Oxygen' before and during "Mach Speed Oxygen Human Bullet" ability is used.
- On the Omake 12 of Season 2, Tadokoro was the 'Ace' for the Team 'Big Eating' competition, but he comes down with a stomach bug. While the first-years managed to assist, they cannot eat all 28 items on the menu in an hour, and Kinjou had to pay ¥24,800 (US$201.50) including soft drinks.
- Another offset ability is "Rampaging Human Bullet Vacuum", where he lets out as much air as he can, then suck the air out of plastic bottles for ease of recycling.
- His family owns Tadokoro Bakery, which was shown making a morning delivery to the Cycling Sports Park during Training Camp.
- Tadokoro Jin also holds the record in Ramen Taro (Sakura Branch) for the fastest person to ever finish an extra large pork ramen at 7.5 minutes.