When Chōji was younger, he was often put down for not being good at a child's game called "Ninja", which appears to be a cross between tag and hide and seek, often using shuriken made out of cardboard. His peers were always berating him, telling him that any team that he was on was bound to lose. One day, they simply refused to let him play at all. Chōji and his father were later seen talking on the roof of a building where Chōji was still upset over the way he was treated by the other children. His father told him that few people have a heart as kind and caring as his, and one day he would meet someone who would see that in him and respect him for it, and that eventually they would be the best of friends. Soon after, Shikamaru walked up the stairs. Chōji recognized him as the one who had defended him earlier. He asked Shikamaru why he wasn't playing the game, to which Shikamaru responded that it was a drag. He then told Chōji that he liked to come up there to watch the clouds and that Chōji happened to be sitting in his spot. Chōji moved over to give him room. Shikamaru proceeded to lie down before telling Chōji that he should watch the clouds with him. This delighted Chōji, and he eagerly asked Shikamaru if he wanted to eat some snacks that he had brought. Shikamaru took him up on the offer, causing Chōji to be overjoyed, then Shikamaru said "This is the best, watching clouds and eating chips". From that day on, the two became best friends.
Chōji is a very kind, polite, and caring person. These characteristics are said to be his greatest strength by both his father and his teacher. He is easily motivated by the prospect of food, and becomes highly agitated when somebody calls him "fat" (he refers to himself as "big boned", "chubby", or "pleasingly plump"). However, he does not hide his love for food and his near constant hunger is also an annoyance to his team-mates, as eating often comes before other necessities such as stealth and teamwork. Food can also make him over-react about silly things, such as who gets the last piece of meat, or when Akamaru tried to take his food, and he refuses to let anyone else eat the last chip in the bag. Chōji has a long-standing friendship with Shikamaru. The two have complete trust in each other, with Shikamaru being one of the few people to look past Chōji's lack of athleticism, and see that he had a kind heart; recognizing Chōji's true strength. Because of this, Chōji has unconditional faith and loyalty to Shikamaru and, if necessary, would give his life for him.
Chōji has brown hair, swirl marks on his cheeks, and like the rest of his clan, he has a much more robust physique than most other ninja. Since his childhood, he has always been quite husky which is a necessity in his clan to perform their techniques since they convert calories to chakra. During Part I, Chōji's wore grey shorts, a rather long white scarf, a short-sleeved green jacket over a white shirt with his clan's emblem on it, ring earrings, and his legs and forearms were wrapped in bandages. His forehead protector was also worn on a bandanna around his head.During Part II, he sports a red top with armour on his torso, arms, and upper legs, similar to his father. On the front of his chest armour is the obligatory kanji for "eat". His brown hair has grown much longer and he also changes his earrings from hoops to the studs that he got as a gift from Asuma.
During the Chuunin Exams, Choji did not make it through after fighting a Dosu. Choji helps Shikamaru train for the finals of the Chunin Exam.
Shikamaru recruits Choji along with Neji, Kiba and Akamaru, and Naruto to go on a mission to retrieve Sasuke from the Sound Four, servants of Orochimaru. When they find them they become trapped in a rock dome by Jirobo. From instructions from Shikamaru, Choji uses the Human Boulder Jutsu on the weakest point on the dome setting them free. Choji then battles Jirobo while the other four go after the rest of the Sound Four and Sasuke. When he battled Jirobo, Choji uses the Akimichi clans special pills. The first one he uses is green. This increases his strength. Next he uses the yellow pill increasing his strength even more. Last is red. This increased his strength 100 times. This also makes him skinnier and chakra butterfly wings. He then kills Jirobo but this leaves him unconscious.
The Search for Sasuke
When Shikamaru asked Choji to come along to find Sasuke he agreed. Later, Shikamaru makes a speech of him not being lazy and him being a leader. Choji knew he wasn’t bluffing. On the way they saw many traps and they catch up to Orochimaru's followers. The followers of Orochimaru catch them and thinks their all weak. Shikamaru uses shadow possession jutsu, and catches them all. But, the follower from the west gate also knew the shadow possession jutsu and broke the jutsu. They south gate follower comes and uses a jutsu that traps them in a rock wall. The wall was draining there chalkra. The team kept trying and trying to break out but, the walls repaired itself. Then Shikamaru figures out that in the back wall it recovers the slowest so he knew someone with great Taijutsu can break it. Choji uses a jutsu that makes him look like a giant ball and he says:
"Bah-Ruu! Bah-Ruu!, Bah-Ruu!"
Soon as they get out Naruto and Akaramu head for an attack, and they were beaten. Choji seemed like the only one who could beat him. Choji tells the others too catch up to Sasuke and he'll handle this guy. the others go of. Choji is winning at first but, the south gate follower used his cures mark level one. He is beating up Choji. Choji takes out these pills that are green, yellow, and red.
Choji vs Jirobo
Choji eats the green one. Choji is still losing the fight, then he takes the yellow one. Then the southgate follower takes it too the next level and turns red and has longer hair, he turns into level two. He is beating him and mocking, and talking about his friends, and he eats the last chip of his favorite chip bag Choji opens the red pill. he says to himself:
"I can't beat him if I don't take the pill, but if I do then I'll die."
He takes the pill. He changes his form, he becomes more skinnier and has now butterfly wings. He beats him up. Choji then focuses his chakra to his left hand and punches him in the stomach. Choji is tired and about to die, then he spots a butterfly and follows it and sees a tree with directions of were the group left, and their is a note. Choji remembers what his father said when he was younger, and knows that he has great friends.
Hidan and kakuzu Arc
Chōji arrived with Ino as back-up for Shikamaru and Asuma in their fight with Akasuki members Hidan and Kakuzu. As the Akatsuki pair fled due to their arrival, Chōji prepared to take the fatally injured Asuma back to Konoha for treatment. Asuma, however, knew that he wouldn't make it back to Konoha, and gave some parting words to his team. He told Chōji that he was a kind-hearted boy, who thinks about his friends, and, therefore, may be a stronger ninja than anyone else, and to simply believe in himself. Asuma also told Chōji to diet a bit more, and Chōji said that, while it was difficult, he would try. Chōji then reminisces his memories with Asuma like the day when they were assigned to him as students and he treated them for a meal and Chōji had ordered a banquet, which hurt Asuma's economy. Chōji then cried. After smoking one last cigarette, Asuma died, leaving Chōji, Shikamaru, and Ino to set out in an attempt to avenge him.
When the remaining members of Team 10 distracted Hidan and Kakuzu, Chōji attacked the two with his spiked human bullet tamk , its effectiveness increased with his new ability to grow and sharpen his hair. Later, when Kakuzu's masks charged at Chōji and his team, Chōji used mega palm thrust to crush the masks and keep them at bay. His attempt was unsuccessful, and Kakuzu was able to pin him down.
Later, after Naruto arrived and defeated Kakuzu, Chōji returned to Konoha with the rest of his team, noting that Naruto's defeating Kakuzu made him "cool", even if not as much so as Shikamaru.
As an Akimichi, Chōji uses the calories he eats and converts them to chakra in order to perform his technique which is the primary reason for his as well as the members of his clan's physical size. Chōji's most pronounced ability is his tremendous physical strength, being the physically strongest member of the Konoha 11. Shikamaru hinted at Chōji's raw power during the Sasuke Retrieval Arc, but it wasn't until he broke them out of Jirōbō's domee that the rest of Sasuke retrieval team believed him. He is also proficient in taijutsu, as seen when he flipped Jirobo, a skilled practitioner of the art, over without seeming to use much effort. He is not, however, particularly fast in his movements.
As an Akimichi, Chōji knows various secret jutsu that allow him to expand body parts to several times their normal size, the most common of which is the multi-size technique . He uses this to perform his human bullet tank attack, where he turns himself into a giant ball and attacks opponents by running them over, shouting "roll" repeatedly as he does. He can also add spikes to this attack to make it more damaging with a chain of kunai. He can also use the partial multi-size technique to expand his arms and legs as well as other body parts.After the time skip, Chōji's Spiked Human Bullet Tank does not involve kunai wrapped around him, but instead involves a technique that hardens his hair into extremely sharp spikes that cover his body, similar to Jiraiya 's needle jezo technique, after which Chōji spins rapidly. Also, Chōji no longer needs to take any pills to perform the partial multi-size technique . He recently learned calorie control technique which allows him to grow his chakra wings without using the colored pills.