From Viz:
Akira Kurusu thought he was doing the right thing when he rescued a woman who was being attacked. Expelled from his school and sent away from home, he is reenrolled in Shujin Academy on probation. Trouble finds him again on his first day when he comes across delinquent Ryuji Sakamoto and the two somehow stumble into a castle in an alternate reality. Caught by the castle’s king, the schoolteacher Kamoshida, Akira discovers his will to rebel and awakens the power of his Persona.

Incorporates the expanded plot from Persona 5 Royal.