Global Lord: 100% Drop Rate - Chapter 55 - 55 Hero Inheritance Secret Manual! Diamond-Tier Scarlet Lord Talent Sphere!

An Individual from Earth finds themselves in the Shinobi World, equipped with a Scientific System. From that moment, he delved into scientific research far ahead of its time.

Sangyan turned into a widow known to bring misfortune to her husband. Despised by her in-laws and disdained by her own family, she volunteered to retire to a remote estate to live out her days. At this moment, she caught the eye of a tyrannical emperor with a strange illness - being near a woman caused him unbearable itching and relentless vomiting.Hence, the 26-year-old emperor had never favored any of his consorts, let alone sired any heirs. The imperial harem constantly pressured him for offspring. The common people also yearned for a royal heir. When they learned that the tyrant held affection for Sangyan, the widow with the ill-fated destiny, the entire nation opposed their union.Eventually, the entire country pleaded with Sangyan to bear children for the sickly and tyrannical emperor...Beauty widow with a deadly fate VS Emperor with allergy to women

Another entry in what you can call the Proto Harem Series: the books written before the Harem Series that take place in the same world.

It’s about a swordswoman whose student is captured, so she goes to rescue her.