Naito Horizon (内藤ホライゾン, Naitō Horaizon), or Boon (ブーン, Būn), refers to an AA character that was a Hitahita variant, but was evidently separated by 2004. He speaks with a '-o' (～お) verbal tic, which used to be trendy on 2channel's /news4vip/ board.

• The 'Boon-Genre Novel' (ブーン系小説, Būn-Kei Shousetsu) is a type of AA story, featuring Boon and several other characters, that would get dropped in a general thread or individual thread.
• He is the same protagonist of the VIP-themed ROM hacks of Super Mario World, the VIP-themed ROM hack of Pokémon FireRed, and serves as a common enemy in Shobon no Action.

• Aramaki Scarchinov and Yaruo - Distant relatives.
• Tsundere

• Naito Horizon on the 2ch AA Illustration Project
• Naito Horizon on Pixiv Encyclopedia
• Naito Horizon on Niconico Encyclopedia