I became the younger brother of the Yandere heroine.

I found myself reincarnated into a video game where all the heroines have Yandere tendencies, meaning they become dangerously obsessed with their love interest and resort to violent and psychotic behavior. However, I am not the love interest of any of the heroines. Instead, I am the younger brother of one of the heroines, who in the game's ending, becomes a ruthless killer, targeting and killing her own family in a fit of jealousy and possessiveness. Knowing the fate that awaits my family, I must find a way to stop my older sister from becoming a Yandere and killing everyone. However, this is easier said than done, as Yanderes are known for being extremely difficult to reason with and often resort to violence at the slightest hint of betrayal or rejection. I start to investigate my sister's behavior and try to find out what triggers her Yandere tendencies. I also try to build a strong bond with her and make her understand that our family loves and cares for her. Along the way, I encounter the other heroines, who all have varying degrees of Yandere tendencies and may either help or hinder my efforts to save my family. As I delve deeper into the game's world and unravel the secrets behind the heroines' Yandere tendencies, I must tread carefully and make difficult decisions that could determine the fate of my family and the game's world as a whole. Will I be able to save my sister and my family, or will I fall victim to the Yanderes' twisted love? N/T: This is not my own novel or translation. I am currently machine-translating the novel, so please do not expect a flawless translation as I am using Google Translate.