Reborn in the Deep Palace and Dotes on the Concubine Alone

Qin Wankuan: What should I do if I am reborn and try to save the Prime Minister Zuo's Mansion, but suddenly find that... I don't seem to have any use for myself? Could it be that the purpose of his rebirth was to inspire his eldest and second brothers to work hard? I only wanted to replace my sister in the palace and save her life, but I didn't expect that I met him with whom I would spend my life together...