Apachai is known as the Muay Thai “Shinigami” and Muay Thai master at the Ryozanpaku. He is also shown to have been trained in Muay Boran, though 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.
Despite his lethal skills, Apachai has a very childlike nature, which is why he is good with kids and animals (he also happens to have the unique ability to communicate with animals). However, when it comes to fighting, Apachai lacks the ability to hold back, and often nearly kills Kenichi (one incident from chapter 24, 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, therefore striking with deadly force has become a reflex for him. Since he was saddened by the fact that Kenichi was scared to train with him, he eventually learns how to hold back his strength, though he still sometimes knocks out Kenichi when he enters his fighting mode.
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.
When Apachai talks he frequently says “Apa,” sometimes even yelling out “Apapapapa” whilst fighting or training. He also answers the phone with a “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.