Hatou, Manabu

A boyish girl who is nicknamed "Gaku" due to how her name is read in kanji.

[Spoiler] She befriends Yukari, who describes her as an "all-purpose robot compatible with many attachments." When her left arm is sliced off by a serial killer, Yukari repairs it using a cellphone, giving her the ability to communicate with versions of herself from alternate timelines and realities under certain conditions. Using this power, Gaku becomes able to travel between these different possibilities, even going back in time and becoming other people in the process. [/Spoiler]