Toaru Majutsu no Index: New Testament - Volume 1, Chapter 4: The Right to Become a Good Person and the Right to Reject It. Black.

The world that nurtured the civilization which reached the pinnacle of magic was on the verge of destruction.
The last survivor transmigrated to the past, when the magic civilization started growing, as countless mages were still fumbling their ways through the thorny paths of magic knowledge.
He, who came from the end of the magic era, aim to reach the pinnacle of magic.

- Description from Novelupdates

Chu Xuan transmigrated to a fantasy world and became the young master of a powerful family. He was rebuked for misbehaving just because he sneezed during a banquet. As punishment, he was banished from the ancestral mansion and was relocated to a remote residence.

He did not mind the punishment at all. He just needed a spot that could allow him to be a shut-in. With the system that would allow him to grow stronger by being a shut-in, the longer he stayed indoors, the more powerful he became.

After being a shut-in for a day, he was rewarded with the Indestructible Body Technique.

After being a shut-in for a month, he was rewarded with the Immovable Mountain Technique.

After being a shut-in for a year, he was rewarded with the Yuxu Celestial Scripture and 100 years of cultivation.

After being a shut-in for 10 years, he was rewarded with the Chaotic Indestructible Body and the Bell of Chaos.

…

Chu Xuan declared, “No one can make me leave my home. I like being a shut-in!”

Cultivating his power by slaying demons and taming countless beasts, the emperor solidified his throne as the world's ruler. But not once in his life had he expected that his disciples would use research on demonology to sap the world tree's power and push the world to destruction.Trying to fix his mistake, he opted to use all of his cultivated power to cure the world tree and block anyone from sapping its power ever again. But in exchange, he was to lose all of his power.But...the worst had happened, his wife... had betrayed him.

Shu Wan, the most outstanding daughter of a high-status family from a feudal dynasty, travels a thousand years into the future, becoming the new lady of the Fu family in the capital.------Her husband in name has gone overseas to explore markets, leaving behind a rebellious son whose name resounds throughout the capital.------Upon first meeting, the rebellious son speeds past on a motorcycle with his silver-white hair flying, “Isn't that my stepmother who's 6 years older than me? Skinny arms and legs, but with grand ambitions.”Before he finishes, Shu Wan leaps up and plucks him off the motorcycle with one hand, “Watch your mouth.”------Fu Yang is consistently at the bottom of his grade, especially with his Chinese language scores never passing 50.Shocked by his atrociously written exam papers, Shu Wan asks, “Are you even Chinese?”Fu Yang is defiant, “Aren't you a dimwitted academic failure yourself, what right do you have to criticize me?”Yet the next second, as Shu Wan smoothly writes down 'Ancient Prose Paragon' with a brush, it's Fu Yang's turn to be astonished.Isn't she a walking dictionary?------Fu Siyu returns from his overseas expansion earlier than expected, thinking he would come home to chaos.However, upon entering the door, he sees the usually defiant Fu Yang sitting obediently practicing his calligraphy with a perfect score exam paper beside him.And his reputedly timid wife, in a sleek black high-slit dress, confidently struts to the music, drawing the attention of everyone.But none of that is the focal point. The focus is on Fu Siyu's gaze, sharp as a knife, directed toward the dance partner's hand resting on Shu Wan's lower back, “Let go.”Note: The son is not the biological child of the male lead.