A Time Better Than This - S. Niragi

NANAMI ASAHINA is very outgoing and confident, despite not having any friends. She isn't the best at school, and would rather focus on her martial arts training. However, she is good at protecting SUGURU NIRAGI- a shy, nerdy kid- from being relentlessly bullied.

After meeting one day under unfortunate circumstances, the two become inseparable. By becoming friends, Nanami starts getting dragged into Niragi's school drama, but that's a price she's willing to pay. Good things can't last forever, and one day Nanami delivers heartbreaking news that she has to move away.

Ten years later, Nanami goes back to Japan in hopes of finding her best friend, but things take a turn for the worst when she is transported to a dystopian version of Tokyo, being forced to play deadly games. Upon coming to this world, she reunites with someone familiar. But throughout the years, they have both changed for better or worse, and they need to figure out how to reclaim what they once had.