Other self

An "other self" is an alternate counterpart to a human character that resides in the Otherworld. Very little is known about them, but it is presumed that huke's characters are of this type.

Possible abilities
An "other self" has some sort of connection or personality similar to that of their real-life counterpart. When their goals become the same, presumably the "other selves" can create a connection to their counterpart and make a deal with him/her to "merge" or "fuse". The only people who have been seen to do this are Kuroi Mato and her "other self" Black★Rock Shooter, but it can be assumed Takanashi Yomi and the Dead Master did the same as well.

It is possible that an "other self" cannot even materialize without merging or taking a body, as Black★Rock Shooter's lips do not move when she talks before she merges, and the Dead Master dissolves immediately upon leaving Yomi's body.

How much control each party has when merged is also unknown. When merged/possessing Yomi, the Dead Master was behaving in a violent, cruel manner, much unlike Yomi; however, it is possible Yomi had lost control or was sharing the Dead Master's angry instincts. However, Black★Rock Shooter seemed to be empathetically reacting to the Dead Master/Yomi in a way Mato would be likely to.

It is also unknown whether there are beings other than "other selves" in the Otherworld; for instance, whom Strength would correspond to is unknown (although Strength is implied to be the "other self" of Yuu), or Black★Gold Saw. It is unknown if Black★Gold Saw is an "other self" at all, and if she is, whom she is one for and how she relates to Black★Rock Shooter or Kuroi Mato. In the train, her other self may have been seen sitting.

"Other selves" seen

 * Black★Rock Shooter
 * Dead Master
 * Strength (implied)