Yesterday's Shadow Tag

Yesterday's Shadow Tag (きのうの影踏み,) is the ability of Mizuki Tsujimura.

Description
Tsujimura's ability is transferred to her by mother. It allows her to create 'baby shadows' and control their strange/curious lives. It most often acts as an automatic response type ability that follows the command placed on it by her mother:

"Kill anyone who my daughter Mizuki Tsujimura tries to kill right before she kills them."

In other words, Tsujimura’s ability will activate immediately when she wants to kill someone and the body shadow will slaughter them faster than she can kill them. Thus, making Tusijmura unable to kill anyone herself. Tsujimura has no control over this function of her ability. Therefore, her ability itself is the one being judged by Yukito Ayatsuji's ability, Another.
 * Baby Shadows (影の仔,): They are usually hidden in the shadows and is seen to have no particular shape. It also takes the appearance of a grim reaper like shadow creature with a scythe when it activates automatically.

Derivation
The ability is reference to Yesterday's Shadow Tag a series of 13 short mystery stories written by published in 2015.