Aja

It's three years after the events of the original Battle Royale, and Shuya Nanahara is now an internationally-known terrorist determined to bring down the government. His terrorist group, Wild Seven, stages an attack that levels several buildings in Tokyo on Christmas Day, killing 8000 people. In order for the government to study the benefits of "teamwork", the new students work in pairs, with their collars electronically linked so that if one of them is killed, the other dies as well. They must kill Nanahara in three days - or die.

All set to enjoy their day off, three high school friends, Yukino, Asako, and Natsu, board a seemingly normal train... when suddenly, a deafening sound and a flash of light envelop them!....But the three arrive at school the next day as if nothing happened. And yet, something is not right....They see oddly familiar faces, their families are out of sync and they are chased by strange men in black. Plagued by these nightmarish sensations, Yukino flees, only to find herself in front of the amusement park they were heading to on that fateful train ride. Slumping to the ground, Yukino comes to a strange realization....They are stuck between nightmare and reality, between the walls of two worlds that are closing in on them. But which world is real...?!"

In a bleak, fictional city, recluse Jun Kawase is visited by his pushy friend, who parades a stream of eccentrics into his room—stirring up old wounds with a childhood classmate and forcing Jun to face the world he’s avoided.