7's7's―セブンズ―; 7's守护凪咲

A pretty girl, Tamura Nagisaki, appears before an ordinary high school boy. When she says, "Will you protect me?", his ordinary life is thrown into a tailspin. The pleasure killer, Dimensional Rider, kills Nagisaki without a motive. With Nagisaki's death, time between the two loops back and forth. Can the two escape the carnage and infinite loops?