Arslan is the heir apparent of Pars, a strong nation that sits at the hear of the trade route connecting the East and the West. When the pagan nation of Lusitania begins an invasion of Pars, the timid Arslan is confronted with battle for the first time. His worst anxieties are realized the Parsian army falls for a Lusitanian stratagem and are routed. He barely escapes with his life, thanks to the loyal and indomitable warrior Daryun. Together they will stand against the invasion and the cruelties of fate that are about to blow down on Pars.

Ren Homura returns to his former residence, yet he feels very uncomfortable: he possesses no memory of having lived there. Without warning or his permission, a game called “Monster Strike” installs itself into Ren’s smartphone; monsters of the game then literally fly out from his smartphone and start fighting on streets. Watching the fighting in amazement, Ren starts picking up his lost memories.