"Originally assumed to be two separate Diary users, Marco and Ai are in fact both the Seventh Diary user. When first introduced, Marco and Ai were using apprentice diaries which were assumed by Yuki and his allies as their real Future diaries with Marco's The Unbeatable Brawler Diary (常勝無敗ケンカ日記 Jōshō Muhai Kenka Nikki^?) predicting attacks before they happened, while Ai's Flirting Diary (逆ナン日記 Gyaku-nan Nikki^?) locates any man she wants to flirt in the future. Their real diaries are the Exchange Diaries (交換日記 Kōkan Nikki^?)which report each other's immediate future. The couple displays excellent teamwork as they use their diaries to cover each other's weaknesses."

"The secondary female protagonist, the Ninth Diary user and the protagonist of the side-story manga, Future Diary: Mosaic. An infamous atheist terrorist, Minene is a young woman who has hatred against organized religion particular God. Her hatred of religion stems from her past when she and parents were traveling in a city in the Middle East but got caught in a battle, which is hinted between Israelis and Palestinians, where her parents were killed in the crossfire. Blaming God for her parents death, she leads a crusade of destruction against those associated with God. Minene got involved in the Diary game when after a failed assassination to kill a Catholic Cardinal, she tried to escape but almost fell to her death but was saved by Deus who gave her an offer to save her if she join his game. Minene's diary is the Escape Diary (逃亡日記 Tōbō Nikki^?), which will chart out the best course of actions for her to escape whenever she finds herself in a dangerous situation. While it means she can escape anything, it is not perfect as the diary can only tell her how to escape if there are favorably conditions that allow her any chance to escape."