Double Holder

Double Holder (ダブルホルダー, Daburu Horudā) is the fifteenth episode of the Future Diary anime.

Summary
Deus Ex Machina invites the Diary Owners to a meeting in the Causality of Cathedral which is his home to clear up the specifics of Eighth's diary: one that can allow ordinary phones to become Future Diaries. Yukiteru Amano, Aru Akise, Kosaka Ouji, Hinata Hino and Mao Nonosaka realize that Eighth's diary is a server hosting a blog that endows others with Future Diaries, in an experiment in which the Kosaka King Diary is destroyed.

As Yukiteru is hesitant to rely on Yuno again, Akise comes up as a plan to fend off a future attack on First. That night, Yuno visits the Amano residence, prepares dinner and leaves, to Yukiteru's horror. Rea Amano does not interrogate her son over his recent running afoul of the law, but asks to be told in the near future.

Nishijima takes the teenagers to Kosaka's large family estate, hoping to cut Eighth's forces' connection to their diaries by remotely turning off the private telecommunications tower. However, Yuno cuts the estate's power, forcing Akise and Kosaka to deactivate the tower manually. Yukiteru binds Yuno's hands to keep her under control as Eighth's forces break through to the main house. Hinata and Mao are subdued by a pair of Apprentice Diary Owners.

After the cell tower is disabled, the intruders, Marco Ikusaba and Ai Mikami, reveal themselves as the collective Seventh Diary Owners, with their Exchange Diaries telling them each others' futures. Yukiteru unbinds Yuno, who is eager to protect her love, in a bid for self-preservation.

Hinata and Mao are taken to safety as Seventh fights First and Second in the now-burning house. During the battle, Marco blocks a stab meant for Ai and berates Yukiteru for not doing the same when Yuno sustains an injury, calling the love between First and Second fake. Seventh makes off with the two teenagers' diaries and Minene Uryuu comes to assist in Yukiteru's physical recovery in hospital, following the fight.

Muru Muru's Section
While Muru Muru is at Mother's Home explaining to Ueshita her role in the survival game, she sets up a trap to trip up the lady, hoping to investigate her strange anatomy. Ueshita somersaults over the demon's tripwire, coming off none the worse for wear. Back in Deus' realm, Muru Muru is still puzzled by the physics involved.