Apachai Hopachai is one of the supporting characters of History's Strongest Disciple Kenichi. He is known as the Muay Thai "God of Death" and Muay Thai master at the Ryōzanpaku. He is also shown to have been trained in Muay Boran and Muay Thai, though he practices it at night only for the sake of upholding the traditional of the fighting style, and even tries not to show it to Kenichi to protect him because it is very dangerous.
As a child, Apachai was brought by a gangster to the crime boss and tested for his strength by the latter, easily breaking the cane sent flying at him and taking out the crime boss and his bodyguards. This action caused his own crime boss to scold him. Soon after, Apachai was bought off the crime boss by Agaard, and left to live in the Romtyphoon gym for the next few years.
Throughout the years, Apachai demonstrated his ability with animals, even finding a "cat" (which is actually a tiger cub) and treating it as his pet. His inability to hold back was also shown as he was seen razing an entire field of banana trees and knocking out his enemies in the underground ring with single clean hits, quickly becoming a fighter of his own level and making it difficult for people to match him up with others. He also promised Agaard that both of them would rise to the top of the Muay Thai world, and even cheered on Agaard in the final round despite knowing that he would be sent to another gym should Agaard win the match.
A few years later, after Agaard left the Underground Muay Thai world to find a "world of true martial arts," Apachai improved his skill in Muay Thai to the point where he blocked a robber's elbow attack with only his pinky. During this time, he found a tiger cub that has grown into an adult, named "Meo", though Apachai still believed is just a gigantic cat. It was also noted that Agaard's promise to feed Apachai still takes effect, as the members of the Romtyphoon gym still put Apachai's appetite above their own based on Agaard's last request. After Apachai returns to his gym, Agaard assaulted him to test his strength, became disappointed in Apachai's delayed training, and told Apachai to join "Yami". This prompted Apachai to set out on his own journey to find himself.
Apachai went on his journey, but quickly starved and did not have access to much food. He ate the hamburger that Hexford dropped for him and paid him back with his services as a bodyguard. However, he remained unaware of the true nature of his employers, and initiated a fight with the invading elder, who matched him strike for strike and continued to fight while dodging bullets. Eventually, Apachai became disillusioned with the child traffickers when he realized their true colors and took out his employers, freed the children, and brought the treasure from the ship to finance the poor village. He follows the elder and Miu until they returned home to Ryozanpaku, after which he becomes a part of the extended family of masters.
Despite his deadly skills, Apachai has a very naïve nature, which is why he is good with kids and animals (he also happens to have the unique ability to communicate with animals). He also looks out for any people he deems his friends, such as the child traffickers he was bodyguarding. He always looks out for Kenichi, and hammers nails into voodoo dolls (a "spell" that Shigure teaches him to bring good luck) whenever he feels something bad will happen to Kenichi. He's also very poor with doing chores which usually leaves what he works on (such as cooking or cleaning) to a complete disaster and he even admitted he sucks at chores. However, after some "secret training" he was working on with Kensei, he's finally learned how to at least do laundry, as Miu noted all the clothes he cleaned are perfect.
Apachai is shown to have looked up to Agaard Jum Sai as an older brother. He has also mentioned several times that he has trouble understanding Japanese which may be another reason why he never holds back despite how much everyone tells him to, though this may extend to languages in general when he is told by Agaard to hold back or that he has not seen the terrifying effects of it until he started to teach Kenichi. He does not like to ride airplanes and, like Kenichi, states how scary something is such as muttering "planes are scary!".
He also is friends with Kenichi's younger sister Honoka, playing Othello with her, displaying an upset mood whenever she is upset, and, strangest of all, will even follow her commands. He usually does whatever kind of game she wants and often is seen playing them with Shigure.
When Apachai talks he frequently says "Apa", sometimes even yelling out "Apapapapa... (pronounced A papapa pa)" whilst fighting or training, often a source of humor in the series. He also answers the phone with "We have your child hostage." rather than a normal "Hello", presumably because of his past in working with child traffickers. Apachai is also a big eater, especially of hamburgers, voraciously gulping down large amounts of food and will occasionally steal some from Sakaki. This stems from his past when he had his dinner taken away by his boss whenever he broke his training equipment.
Though Apachai is childish, rather thoughtless and naive, he has proven countless times to be very kindhearted, selfless, brave and very peaceful and loving. He loves the minor things of life and has a love of animals, as they always tend to gather around him due to his peaceful nature. Even children love Apachai and so does he, as he enjoys playing with them and hanging around the children.
Apachai Hopachai is a extraordinarily strong fighter with great strength, even when he tries to hold back. Having mastered Muay Thai and ancient Muay Boran from his younger days, Apachai has great skills in the arts. Even against other master class opponents, Apachai doesn't need to use his full strength and can take out several enemies without using much effort. When fighting full-out, he has repeatedly been held back by his companions as he quickly overwhelms them to the point they could die as when he trains with Kenichi on numerous occasions he ended up nearly leaving the boy on the death’s doorstep on more than one occasion. Though he's a Dou fighter, Apachai has been able to keep himself calm in battle and once he fights all out his Ki is dangerously powerful that so much it caused Kenichi and even the normally calm Kokin to become frightened by his and Agaard’s Ki against each other. His skills are so advanced that against Yami member Agaard he was able to win and even survive the hole in his torso and able to defeat the Bantou Master with his wound, which is a testament to his skills.
- Master Thai Kickboxer: Apachai is considered a monstrously powerful master of both Muay Thai and Muay Boran, a title he shares with Agaard Jum Sai. As a master of both styles, Apachai is an incredibly powerful close range fighter, capable of overpowering most of his opponents without so much as an effort. When he does go all out, he is able to fight and overpower people like Agaard Jum Sai, to the point where even Agaard was surprised at how strong he was. Apachai has mastered regular Muay Thai to the point where his close combat abilities make him almost unbeatable to the normal master class fighters (an example being that he managed to hold his own against Hayato Fūrinji himself for a short time before eventually being overpowered). Also as a master of Muay Boran, he has mastered a number of ancient Muay Thai techniques and styles, giving him a larger arsenal of attacks to use, though he normally tends not to use these techniques due to how dangerous they are. He even practices it at night in order to prevent Kenichi from learning any of it. He will only resort to using Muay Boran against dangerous fighters in the event of a life or death battle, the greatest example of this was during his battle with Agaard Jum Sai. His mastery of both styles is so great that he, along with Agaard, have mastered the secret technique Bolisud Look Mai and he even created an extension of that secret technique himself.
- Innate Talent: From a young age, Apachai showed great physical prowess and natural talent for combat. Even as a small child, he was able easily defeat several thugs without even a scratch. His natural aptitude for combat continued to show its brilliance as he continued to grow, quickly becoming highly proficient in Muay Thai and Muay Boran. Apachai is also shown to be able to quickly learn skills he truly sets his mind to, such as becoming good at Othello in wanting to beat Honoka. In doing so, he can easily defeat most of Ryōzanpaku's masters and only narrowly lost to the immensely intelligent Akisame.
- Immense Strength: Even when only a child, Apachai possessed tremendous physical strength. Whenever practicing on trees and such, he would always end up destroying them. From a stationary position, Apachai can jump several feet into the air and across several city blocks. When confronted by the prospect of riding on an airplane, Apachai can cling to a steel pole with enough force that even Sakaki and Akisame together were incapable of prying him off. Unfortunately, when it comes to anything remotely combat related, Apachai initially lacks the ability to hold back, and often nearly kills Kenichi (in one incident from when he first trained him, Kenichi had to be revived with CPR due to cardiac arrest from an attack by Apachai). The reason for this is because Apachai has been fighting life or death battles in the ring since he was very young, making deadly strikes a reflex for him. When he was younger, he was able to send people flying, and on one occasion, a car flying. Over time however, while training Kenichi, Apachai’s devotion to teaching Kenichi Muay Thai and protecting him has gradually given him control over how much strength he exerts, now rarely even knocking out Kenichi. Even his former mentor Agaard acknowledged Apachai's new control. Likewise, Apachai has insane leg strength, as he is able to easily leap several hundred meters into the air, can also kick stone statues extremely high into the air and punch through the floor just by stepping down on it.
- Immense Endurance: Befitting his large figure, Apachai has a high amount of endurance, such as taking several blows from Kei Retsumin and recieved little damage. Even when he was dealt a fatal blow from Agaard with having a hole in his torso, he was able to revive himself and defeat the Bantou Master with the injury and was able to survive thanks to Akisame arriving and saving him, though it should be noted that had Akisame not arrived to treat him, Apachai would have died from the blood loss.
- Immense Speed: Apachai has regularly shown remarkable speed that defies his bulky built. He is able to launch a huge barrage of strikes in seconds, ultimately allowing him to pulverize stone into dust. He can also close a considerable amount of distance in an instant, giving the appearance that he teleported to untrained eyes.
- Animal communication: Apachai's innocent and adorkable demenor has given him the ability to get along with animals in a harmonious manner, birds will land in his hands and other animals will come right up to him to be petted, even dangerous ones such as tigers are as tame as house cats with him. He has shown that he can talk to the animals as easily as people several times, and that he can understand them as easy as humans.
- Pteromerhanophobia (Fear of flying): Apachai has a crippling fear of flying, leaving him unable to travel quickly by plane.
- Naivity/Childlike Innocence: Apachai can be extremely gullible at times, and is apparently unaware of the illegal activities he has taken part in over the years, such examples are him answering the phone with threats, and protecting a slavery ring without any idea of what it was. This can lead him to be easily manipulated.
- Difficulty Restraining Strength: Since an early age Apachai has been taught never to hold back any strength during a fight, so has difficulty when told to do so later. As a result, he is seen often damaging property and severly injuring people when trying to restrain them or simply spar with them. At the peak of this problem, he literally killed Kenichi during their first sparing session. He somewhat overcame his situation when he was told to treat his disciple as he does children when he looks after them.