In Crystar, players take on the role of Rei as she battles through Purgatory to save her sister. Along the way, she is joined by four other playable characters with whom she can switch freely between. As players progress through the game's story and uncover each character's pasts, they will learn about their individual sorrows and come to understand why Rei's mantra "for when I weep, then I am strong" holds true for them all. The game combines elements from action RPGs with a unique narrative structure that allows players to explore their own emotions while fighting against monsters in Purgatory.