In Version 6.23, the ability to rename the main character introduced a number of cheat codes. Renaming Hiroshi to any of these special names alters the gameplay in some way.
Upon beating the game, one final dialogue box appears where Hiroshi reveals a single code. Subsequent completions of the game will prompt Hiroshi to reveal other codes.
In Version 6.23, the player has the option to rename Hiroshi at the very beginning of the game. If the player chooses any of the following cheat codes for a name, the game will be changed in some way.
In this mode, The blockman oni replaces all of the random encounters in the game. However, scripted encounters such as when the Oni appears in the Piano Room still use the regular Oni.
In this mode, characters appear as they would in South Park. This provides a new, shorter story, which adds blood, comedy swear words, and additional character development. This is harder since The Oni chases you at the start and already kills Mika. The north door is unlocked, but there's nothing in interest.
In the gameplay, Hiroshi, Mika, Takuro and Takeshi approach the mansion. They enter at the main area, where Takeshi tries to escape, only to find out that the door is locked. The Oni then appears behind Mika and strikes her head off. They then exclaim, "Oh my God! They killed Mika!" hence the South Park saying, "They killed Kenny!". Takuro exclaims, "You bastard!" and the remaining characters run in different directions. Hiroshi is chased by the Oni and later lost track of after returning to the main area. Once going to the top hallway and entering the room at the front of the hall, Hiroshi meets Takeshi and Takuro. There is long conversation, and Takuro says, "Calm the F**k down Hiroshi! We'll find a way out of here. Right?" Takuro is standing in the middle of the room when the Oni appears and pulls his head off. The phrase above is used once more, and Hiroshi is once again chased. Hiroshi goes back to room that Takuro died in, and then finds the 'Entrance Key'. The Oni is lost track of and Hiroshi meets Takeshi on the top floor. He talks to Hiroshi, and his head is bitten off by the Oni. As Hiroshi tries to run, Takeshi then stops him. Takeshi has turned into the Oni, and begins to state questions that the Oni had. Hiroshi then runs outside the mansion and meets a man. The man says, "It's the Aooni! It's coming right for us!" and proceeds to shoot his head off. The man asks, "Hey boy, are you ok?" and Hiroshi replies, "I'm saved!"
In the epilogue, Hiroshi states: "If there's one thing I learned from all of this... It's that when you go to an empty mansion on the outskirts of town that everyone says has monsters in it, nothing good can ever come out of it."
In this mode, The Oni cannot harm you. Getting a game over screen is impossible except during deaths from scripted sequences, like forgetting to close the cell door behind you, or the Oni Room sequence. You get this code when you beat the game with HIROSI cheatcode.
In this mode, the character's pictures in text messages are the same as in the earlier versions of Ao Oni. This is the first code you get in the game.
When The Oni chases Hiroshi, a timer appears on-screen showing how long the chase will last for. It is different for every room and shows that if you go to a different area, the chase will last one second longer, and that certain chases last for different amounts of time. There are also random chases.
There will be a guy in the kitchen resting in the sofa. JMU is a reference to the translator of Ao Oni. If you make Oni chase Hiroshi to the kitchen and cease chasing, going back to the kitchen will make him turn into The Oni.