Before she was cursed, she wore a white kimono with a Sakura print, she had black hair with a red headband, and a shadowed off face.
In her monster appearance, she wears a pink hat, she has pale, white skin, she has visible veins in her arms and feet, and wears a white dress. Her face has visible mascara tears with a wide grin plasted on her mouth.
During the Halloween Event, Hiachi’s appearance changed. It is different compared to her in normal mode. Hiachi’s overall model has a striking resemblance to Sama. The eyes of her face are pitch black, and her eye pupils are glowing red. Her mouth is paired with Shinigami's necklace, which are a darker shade of red. This is because she has been possessed by Shinigami, though, this is only limited to the Halloween Event (also, please note that Shiniachi has no impact on the canon storyline, as she was mainly just for the Jigoku Event). She will be much faster.
In the first part, she makes an appearance in La Quinta Highschool, the sewer, and The House Of Death. She's the monster inside the first maze of Chapter I, before entering her maze, you get a jump scare when you come into contact with the bridge.
She appears in the cave where the ancestors heads are at, her head can be seen on the walls.
Before her AI was updated, players could outrun her easily, but when her AI was updated she and the player will gain speed upon notice.
In the time of the great Edo Period, Hiachi was a frail yet playful little girl. Hiachi loved her mother, Futaomote, very deeply, although she wasn't the best at times. Futaomote would sometimes let her impulsive feelings get the best of her, and abuse Hiachi or break objects. But Hiachi still loved her. The village had shunned both of them. They considered the little family... insane. It was difficult living in that kind of lifestyle, especially while raising a beautiful eight-year-old daughter.
Meeting The Unknown Doll
Hiachi was very lonely, as she had no friends to play with. However, her mother, Futaomote, found a little doll in a Sakura Forest. Her mother gave it to Hiachi. She instantly loved her, and she named her Shaku. Shaku was Hiachi's only friend. from the beginning till the end. Hiachi would always enjoy playing with her doll, talking to her as if she were an actual living being. Well, little did she know that her doll was a human before.
The Girl And The Witch
Hiachi was out in the woods playing with her doll when suddenly, the ground shook. She ran and ran until she slipped through a crack which caused her to faint. She woke up in a cave bathed with pink and red, she explored the cave and saw a black figure in a vast sakura tree.
Hiachi asked who it was and the figure responded that she had no name. Hiachi named her "Sama" as her appearance resembled her mother. Sama befriended Hiachi and one day, Sama asked her "My dearest Hiachi.. can you please take this paper off the tree so we can move about freely? I promise you eternal joy". Hiachi then took off the paper little by little, suddenly, she fell down and Sama laughed at her, her vision became dark and she had become one of Sama's puppets.
- In her first jumpscare found in the school, Hiachi will appear standing as she twitches her head while ominous music plays in the background. If the player were to touch her, they will die.
- The second jumpscare is in the sewers. You will find her crying loudly, going near her causes her to disappear as a haunting tone plays in the background.
- Her third jumpscare is found on the bridge to her maze. Before the player approaches the maze, static will be heard as her face appears, standing violently while grabbing the screen.
- In her last and death jumpscare, when Hiachi kills you, she will shake her head left to right here.
- Hiachi's monstrous form is based off of the popular Japanese urban legend 'Hachishakusama' along with her design.
- She is the very first monster encountered in the game.
- When she was alive, she was a psychic, which is a reference to the famous character Samara Morgan aka Sadako Yamamura from The Ring.
- Before she was controlled and turned into Sama's puppet, Hiachi’s accessory was a red headband. However, when she was cursed and claimed by the "friend" she slowly loved as a family member, her headband became a pink hat with a red ribbon, which might either reflect Sama's betrayal or to resemble the form Sama took when they first met each other.
- Before her remodel in the remastered version was released, Hiachi didn't have visible veins in her arms and the pupils in her old jumpscare were glowing red.
- Hiachi’s monstrous form bears resemblance to a Kuntilanak/Pontianak, which is a female vampiric ghost who died while either being pregnant or during childbirth, from Malay folklore.
- According to a lore writer, Hiachi didn't fully release Sama from her eternal seal.
- Few fans have theorized that Mariachi was her biological father due to having the same last 5 letters in their names and he looks quite similar to Hiachi. However, it was debunked by the official lore writers.
- Her death sound is from SCP-173's Horror1 sound.
- Hiachi’s humming is based of from the humming girl in Little Nightmares. 
- Before going into Hiachi’s maze, you will encounter a large city resembling a modern day city in Japan, there are restaurants, and other cosmetics shops around the city, it has an eerie feeling and dark fog covering it
- Hiachi met Sama because of the unexpected calamity.
- She has a disorder just like Futaomote, confirmed by lore writers. Many believe it's autism, however, it is unconfirmed what exact disorder she has.
- When she is chasing a player, one of her eyes grows into a eyeball with a small black pupil, unlike her normal form whose eyes are fully black.