Save a Failed Idol's Life - Chapter 162:

A master of Chakra Cultivation sacrifices everything - only to be reborn with a second chance.After giving his life to save his world, Alaric awakens in the body of a child. In this new realm where power is measured in tiers, bloodlines, and the strength of one's oaths, Chakra Cultivation is an unknown path.As Alaric purifies his chakras, each one unlocking profound abilities across body, mind, and soul, he gains an edge no native warrior can match. But his true test awaits in the Tower of Trials—a rite of passage for the world's young elites, offering immense rewards to those who can climb its treacherous heights. No one has ever reached its highest levels.If mastering his reborn powers wasn't hard enough, his journey will forge a bond with an entity of unimaginable strength - and lead him to lands where no mortal has dared to tread.

Chen Sha came to a world of immortal martial arts and was ordered to take charge of the world’s first sect.

Before his death, the previous chief told him:

“If you don’t become the best in the world for one day, you are not allowed to go down the mountain for one day.”

So he closed himself in painstakingly, crossed the heaven gate in his body, and faced off against the ancient and modern powerhouses…

…

Many years later, Chen Sha recalled the day he went down the mountain,

From the moment he descended the mountain, he was number one in the world.

In the next ten epochs, any gods and demons have returned, immortals and Buddhas have lived in the world, ancient powers and ancient gods have appeared one after another.

No matter how the times change, he has always been No. 1 in the world and has never changed.

- Description from novelbuddy

In the fantasy world ruled by Matriarchy, Kael of the Ancient Moonstone House, was working as a guild receptionist. Throughout his life, he was protected by his mother and later, younger sister, who was considered one of the highest potential individuals in the Queendom of Elyria. One day, he hears that his sister has gone missing and his family has accumulated debts of over 127 million gold coins to the Bank. The Queen comes to his rescue, paying off his debts and in exchange, he has to marry her five daughters, who each excel in a domain of their own.Having the five imperial princesses and the Queen herself as the backing, Kael has become one of the most protected individuals in the Queendom. Little did his wives know that Kael had another identity. He is the most dreaded yet noble Assassin of the imperial city, “K,” one who hunts down the criminals who escape punishment either because of insufficient evidence or using their connections.Follow Kael's journey, as he navigates his life as the protected figure in the light and protector of justice in the shadows.

She, a renowned assassin of the 21st century, actually crossed over to become Su Manor’s most useless good-for-nothing Fourth Miss.