It is August 12th. After the remote control to his boarding house's only air conditioning unit is inadvertently destroyed by spilled cola, "I" devises a plan to return to yesterday in a time machine to recover the remote before it breaks. However, his prankster friend Ozu cannot resist playing with past events, even if it means bringing the universe to the brink of destruction. Now "I" finds himself racing through time to avoid disaster.
Yuta Okkotsu is a nervous high school student who is suffering from a serious problem—his childhood friend Rika has turned into a curse and won't leave him alone. Since Rika is no ordinary curse, his plight is noticed by Satoru Gojo, a teacher at Jujutsu High, a school where fledgling exorcists learn how to combat curses. Gojo convinces Yuta to enroll, but can he learn enough in time to confront the curse that haunts him?
Although traumatized by witnessing the murder of his parents by one of the Choushuu, Ichimura Tetsunosuke's thirst for revenge leads him to desire strength. At the age of 15, Tetsunosuke approached the Shinsengumi, wanting to become one of its members. However, Tetsunosuke lacked the skill, mind, and will to emotionlessly cut down whoever threatened peace and the Shinsengumi. Even with the support of his brother Tatsunosuke and his newfound friends of the Shinsengumi, little did Tetsunosuke know the blood and pain he would have to face being part of this historical group.