Elf Tensei Kara no Cheat Kenkoku-ki - Chapter 11Book 1: -2: Crossbow

A Japanese salary man was reincarnated in a different world with swords and magic. He reincarnated into the family of a powerful noble. One day when he became twelve years old, he was suddenly summoned by his father.

「 I do not mind whether it is a woman in the town or a maid in our house, learn about women.」

Having gained the permission of his father, he uses his power as a noble to have his way with women.

However, he did not know that he was not raising just a harmless pet, but a biological weapon secretly made by the government… a real monster.

As a former librarian, Rand felt that he had been living an ordinary life, the one that he had reclaimed unconsciously every single day.

Recently, he has been a little upset because the pet fish he accidently brought home to raised seems to have undergo some strange changes

Well, it turned into a merman.

- Description from Novelupdates

The first time they met they had battled fiercely, just for a mere bunch of herbs. She needed it to save people, and he wanted to use it to save his own life.

“Let go of it, or you will die.” The man’s violet eyes were cold and sinister as he said in a low voice.

She held on tightly to the base of the herb and pulled its roots right out of the ground, before she turned her eyes back with a crafty smile. “It’s mine now. Snatch it from me if you can.”

When they met several years later they were no longer on opposing sides in hostility. In order to repay the debt for having stolen the herb back then, she went on to miraculously cure his body’s condition, relieving him of the inhumane torment that wrecked at his body day and night. He was amazed by the godly skills in Medicine she possessed and his heart went on to fall irrecoverably head over heels in love.

- Description from novelupdates

Wang Zhong arrived in an alternate world and became embroiled in this world's global war.What he gained was a cheat, akin to a real-time strategy game's overhead perspective, and he could even see through the eyes of his subordinates' units!So, he decisively started micro-managing, “Shift the machine gun position five centimeters to the left! Place the anti-tank cannon in the forest on the right!”Three years passed in this manner, and Wang Zhong looked at the marshal's baton in his hand, then at the double-headed eagle flag behind the emperor's envoy.“In my hometown, there's an old saying, 'Princes and generals, are they not sprung from the masses?' Envoy, do you know of it?”