Jon (木ノ下 Kinoshita ) is a character that makes a cameo in Ao Oni Version 6.23. He will appear only if the player changes Hiroshi's name to JMU (a reference to the alias of the English translator for the game as seen in the game credits).
Jon can be found apparently sleeping on one of the couches in the kitchen in the beginning of the game. If the player chooses to interact with him, he will comment on various things such as traveling to Osaka and "wondering if there's anything good on YouTube."
Turning into an Oni Edit
When the player is chased by the oni, if they decide to flee to the kitchen, the oni will initially pay no apparent attention to Jon. After the chase is over, if the player returns to the kitchen, Jon will transform into an oni himself and chase the player. Jon makes no more appearances for the rest of the game after this point.
It is unknown how Jon transformed into a monster despite not being killed, so the reasoning that the oni has to kill a person for them to become an oni is debatable (another instance of this is when Takeshi hangs himself after feeling overwhelming guilt for bringing the group to the mansion); it has been speculated that he is the manifestation of a previous resident of the mansion. Jon could also be an easter egg that the player can discover by completing the game in under 30 minutes.