By Heart follows Catherine as she tries to figure out a way to hold on to her American roots and identity, after being brought to Taiwan due to her parents' separation, by resisting an indoctrinating Confucian text she has to memorize at school.

An unknown disease is striking to younger generation, the patients are going to lose the sense of reality and the memory of themself. We following a girl who got her new name 'OK' and she is going to figure out what's going on.