I Only Wanted to Cuddle My Sister, How Did I Become the Supreme Master?

Reborn into a magical world with memories of a past life spent devouring anime, our protagonist awakens as a girl with the mysterious "Beloved System." What starts as shock at the gender swap quickly transforms into an obsession with her gorgeous older sister's warmth and affection. But while she's busy being a clingy little sister for years, something unexpected happens—the doting sibling everyone thought was just a cuddly airhead has somehow become an unrivaled powerhouse. How did endless sister-snuggling sessions lead to becoming the realm's most formidable master?