Marco Ikusaba & Ai Mikami

Marco Ikusaba (戦場 マルコ, Ikusaba Maruko) and Ai Mikami are the Seventh diary owners, sharing their positions with the love of each other, and one of the characters of Mirai Nikki. Marco, a skilled street brawler, is devoted to Ai and they work as a perfect battle couple, using the "Exchange Diary" to help one another in the survival game. They wish to become Gods so they can be together for all eternity.

Personality
(Marco) Marco can come across as a typical street brawler, appearing quite cocky, energetic and always ready for a fight. He is quite proud of techniques, particularly his cross chop move. Because of numerous fights he got into as a teenager, Marco is a skilled fighter, being quick on his feet and good with his fists.

Marco is devoted to Ai, having made a vow to protect her during their high school years together. Working together, they consider their love to be perfect and unbreakable. Marco becomes particularly outraged by the actions and cowardice of Yukiteru Amano and he fails to protect his girlfriend Yuno Gasai from his and Ai's attacks, Marco willingly putting his life on the line to protect Ai. He tries to man up Yuki so he can protect Yuno, acting as a foil to Yuki and Yuno. Marco is very concerned over his appearance in his adult years, having long hair which he stylises into a curled cone shape resembling a perm or a pompadour hairstyle, and often carries a comb around with him.

(Ai) Ai is a beautiful, blue-haired, purple-eyed woman, and the long-time lover/wife of Marco Ikusaba. From a young age, she loved Marco after he befriended her and gave her a family after she was abandoned by her parents as a child. She is very devoted to him, and together they form a strong battle couple. Ai is implied to be a flirtacious person, since the Apprentice Diary she gained, the "Flirting Diary", involved identifying the men she would flirt with. She seems to be at peace with Marco's constant fights,

Despite participating in the survival game, Ai and Marco have morals. Ai takes sympathy towards Tsubaki Kasugano, the Sixth diary owner, although she expresses the knowledge that sooner or later that Tsubaki would turn into an enemy if she and Orin Miyashiro had helped her with her troubles. Ai and Marco also refuse to take a life that they do not plan to, treating the wounds of Hinata Hino and Mao Nonosaka who Ai had injured with her knives.

Diary & Abilities
(Marco) Marco and Ai share the Exchange Diary, which doubles as two mobile phones. The diaries record everything Marco and Ai, focusing on each other in a similar light to how Yuno's "Yukiteru Diary" works. If one of the diaries is destroyed, the owner will disappear and not both. The main strength of his diary is that depending on which he's using he can read both about himself or about Ai, but he prefers to read Ai's future rather than himself, which allows for the duo to become a fearsome team. The main weakness of this method is that if the two are by any chance separated then they are obviously unprotected. Marco is given an Apprentice Diary to use to hide the fact he and Ai are Seventh, having The Unbeatable Brawl Diary, which predicts the moves that his opponents will make and how he will defeat them. This is specially useful to him as he's an experienced street brawler and can easily knock out his opponents with this method. Given that this diary depends on its connection to The Eighth's diary, it is vulnerable to jamming, rendering it useless. However it has the advantage that if it is destroyed he won't die.

Being the longtime brawler since a young age, Marco not only possess above avarage physical strength, agility and reflexes, but also has a high pain threshold, evidenced by how he could fight Yuno despite being stabbed on his arm, and also uses a rather unorthodox fighting style, being able of parrying a knife with his teeth.

(Ai) Marco and Ai share the Exchange Diary, which appears as two mobile phones. The diaries allow Marco and Ai to predict each other's movements, and can protect each other when in a fight. If one of the diaries is destroyed, the other owner remains alive. The main advatange of this diary is that depending on how it is used it can predict her own future or Marco's. Using the latter method she can predict anything related to Marco and protect him and vice-versa, creating a fearsome combination. The main weakness of this method however is that if the two are seperated, then they are obviously unprotected.

She was also an owner of an Apprentice Diary known as the Flirting Diary. This allowed her to know with which male she's going to flirt next. The rather only use this diary has is to track foes, so as long as they are of the male gender, but nonetheless useless if they are female and for the game's sake if said males are not participants. Like all of the Apprentice Diaries, hers depends on her connection to The Eighth's diary. If there is jamming then it is rendered useless. And also she won't die if this diary is destroyed because it is an Apprentice Diary.

She's also a skilled knife thrower. She keeps a collection of throwing knives in her jacket, and can throw them with pinpoint accuracy. However, she only has so many and is bamboozled when Yuno Gasai is able to deflect them all. Nonetheless during the events of Future Diary: Mosaic her accuracy is so precise that she's one of the "three" main reasons why the Sakurami Beauty Contest (one of trials) is boring, being always the victor in throwing.

Although not being a brawler like Marco she does seem to have above average skills of her own, as she could restrain Yuno in a proper manner (that is putting her on the floor and restraining her from above) as well as fast reflexes, being able to avoid a dart thrown by Yuki, albeit with warning from Marco.

She also seems to be knowledgeable in other things like infiltration, first aid and parachutes.

Trivia

 * Marco is named after Mars, the Roman god of war. The Kanji characters in his surname 戦場 means 'battlefield', a nod to Mars.
 * Marco and Ai's character theme song is "7th Heaven" by Yousei Matsui and Choucho.