What Comes Before the Slap Is My Sister's Fragrance

Sibling Love, Pretending to Be Good, but Actually Being Gloomy and Bad, Pure Love, Delicate Feelings

Do you have any recommendations for sister-brother romance novels? The younger brother pretends to be good on the surface, but is actually gloomy and evil. He pretends to be good because he doesn't want to be disliked by his sister, and is purely in love. Don't be yandere, don't be yandere, don't force, don't force.