Hokutomaru is one of the heroes from Fatal Fury series.
Hokutomaru is a ninja who is the only pupil of Andy Bogard who has lived most of his life in remote mountains. Andy had would be retired from the fighting scene to teach Hokutomaru. When Hokutomaru was about to complete his training, Andy was sent him to Second Southtown so he could enter the "King of Fighters: Maximum Mayhem" tournament. Hokutomaru didn't win the tournament, but he can made his master proud, so Andy sent him a letter saying that he doesn't see Hokutomaru as a student, but as a rival.
In The King of Fighters 2003, Andy was absent to take care of Hokutomaru, who was sick. Andy was absent again in The King of Fighters XI to train his student.
The fifth Days of Memories establishes Hokutomaru as being biologically related to Mai, though a clear cut family relation for them isn't established. She is also looking after him while juggling her makeshift identity and her nighttime banditry. Hokutomaru frequently runs away from her apartment, causing Mai to worry for him.
If the player wishes to have the route focusing on Mai's day job, they have to select the text options that ignore her nighttime SHIRANUI alias. Doing so will follow a story path that has the protagonist look for the missing Hokutomaru to support Mai. As he tails Hokutomaru, he eventually discovers that Mr. Big is bullying and extorting Mai; Hokutomaru is quite trying to figure out ways to protect her on his own. Though the boy is initially cold towards the photographer, Hokutomaru warms up to the protagonist once he realizes that the protagonist genuinely cares for him and Mai. Hokutomaru then starts calling him "Big brother" as a show of respect.
The good ending for this path ends with Mai and the protagonist getting married; they happily continue to look after Hokutomaru together. The bad ending has Mai and Hokutomaru move away, leaving behind a single letter thanking the protagonist.
Hokutomaru is a boy who was grew up in nature; that his best friends are the mountain monkeys near his training grounds. He knows nothing of the civilized world, being excited and confused by life in a big city. He is a brash kid who doesn't like to be treated as a child. He's very noisy and often acts before thinking, but he has a strong will. Though he is obedient to his master and admires Andy, Hokutomaru clashes with his "big sister" Mai.
Fatal Fury/Garou Densetsu
Art of Fighting