After My Departure Three Repentant Brothers

The protagonist lives in the shadow of her adoptive sister (or lost sister). Her three older brothers always treated her with indifference and even reprimanded her unfairly to defend the newcomer. Even in moments of the protagonist's true medical emergency, they completely ignored her. Tired of the abuse and not being valued, she decides to cut ties and leave. Only after his departure do the brothers realize everything they did wrong. As they try to find her and ask for forgiveness, they discover that she has managed to forge her own path and is triumphing, leaving them in a state of deep guilt as they realize that they have lost her forever.