Kujibiki Tokushou: Musou Hāremu ken - Chapter 68

In this world, orphans or just anyone without any hope for this world can apply to become a “walking target”. Their sole purpose is to be a practicing dummy for the students of the sect who train to become “Demon Hunters”. These students need “walking targets” to test their training on living, walking beings of flesh and blood.
In exchange, they will be provided with food & shelter.
Their existence value is lower than a slave, but if they manage to survive a few years they can receive a life long pension.

Xiao Han is such a “walking target”. One time he witnessed a powerful Demon Hunter disposing a demon. When the demon died, a fragment of the demon that managed to escape entered Xiao Han’s heart. No one saw that, and even Xiao Han himself only felt some discomfort for an instant.

But that thing in his heart soon gave Xiao Han visions, and the first one is of a cultivation method which allows Xiao Han to absorb damage to enhance his body. A perfect cultivation method for a “walking target”.

- Description from Novelupdates

He became a teacher at the best magic academy in the empire.
….For being mistaken for someone else.

Back in 1996, when the daughter of the Old Xie family, Xie Wanying, said she wanted to be a doctor, many laughed.“Phoenix begets phoenix, dog spawns dog. A truck driver’s daughter becoming a doctor is as likely as a sow climbing a tree.”“I’m not just going to be a doctor, I’m going to be a female chest surgeon,” said Xie Wanying.Her words provoked even greater waves of disdain within the doctors' community.Relatives who were doctors ridiculed her mercilessly: “Do you know how high the admission scores are for medical students? Do you think you can make it?”“There are zero female chief chest surgeons in the country. Who do you think you are!”A bunch of people mocked her: “You'll probably only get into a third-rate medical college and end up as a health worker in a small county town. It's easy to imagine what sort of marriage you'll have.”After the college entrance exams, Xie Wanying entered the top surgical class in the country with the highest science scores in the province, with department heads in the Capital’s top-tier hospitals vying for her from her internship beginnings.“Student Xie Wanying, come to our digestive surgery department.”“No, she must come to our urological surgery—”“Pediatric surgery is in short supply of female doctors like student Xie Wanying.”Circles of relatives and friends: …At this time, Xie Wanying independently completed the youngest Tetralogy of Fallot surgery in the country, represented the national association of chest surgery at an international medical forum, and published the world’s first minimally invasive heart valve repair surgery, becoming truly the foremost surgeon in the field of female surgery!As for the marriage concerns that everyone “worried” about:A brother from the Returned Overseas Faction, a hot bachelor within the Capital, changed his QQ profile picture to Junior Sister Xie.The young CEO, a handsome man, came to the hospital every day with flowers, keen to offer a diamond ring.Not to mention, a whole host of suitors had long since worn a path to the Old Xie Family's doorstep...