The heroine is a demon and doesn't understand love. The male protagonist is in love with the Brain Sword Master, but no one understands why the male protagonist likes the female protagonist. The male protagonist is passionately devoted to the female protagonist (even if he loses his love and memory, he can still feel that he likes the female protagonist based on his body memory)
The male and female protagonists are a pair of childhood sweetheart NPCs in a love game. The female protagonist is the guiding NPC, and the male protagonist is the main controller.