Tyrannical Prince, you're just so-so!

She was the famous assassin princess of the underworld, and he was the top prince of the underworld. What kind of sparks would they create when they were together? The things behind their families were pulling them along. Could he really escape unscathed after entering the underworld? Would they agree to their parents ’request? Would they agree to inherit the family? What would they do in the face of their family’s marriage? His closest brother had turned into his most hated enemy. His childhood friendship had turned into hatred. Could he really blame the tragedy of the previous generation on the next generation? What kind of setbacks would their relationship experience?