Gimai Seikatsu - Days With My Step Sister - Chapter 6:

I just left an honest review, and I was reincarnated. But not into the novel I criticized—into the world of [SSS-Class National Power Heir] .I reincarnated as Baek Seo-jun, the older brother of the original protagonist, faced discrimination, and was discarded as a sacrifice.And then I experienced hell.With the power of the final boss, I will exact revenge on everyone—whether it’s the original protagonist or the villains.[The protagonist who has gained the power of the final boss]

One of the few self-cultivator who exist in this modern world; due to an unfortunate event, completely destroyed his body in an explosion. Using all his effort to save his primordial spirit, he ended up in an strange magical world and had to start all over again. From a fallen aristocrat to the Warlord of Chaos, this can no longer be summarise as legendary; this is the life of the God of War.

- Description from Novelupdates

After five years, Ning Xi has returned and is out to take revenge on the sister who turned her parents against her, and the childhood sweetheart who betrayed her for her sister. She aims to fulfill her childhood dream and become a famous actress. However, her sister is still out to get her and she has to avoid all her underhanded schemes.

One day, after falling into one of her sister’s schemes, she meets an adorable little boy and saves him. His father then offers to repay her with his body: “Marry me.”

Ning Xi: ???!!!

Little boy: -sad puppy dog eyes-

Thus Ning Xi starts staying at the mute little boys’s house to help him come out of his shell… cue lots of comedy, some flirting, sweet moments between Ning Xi and little bun… and maybe big bun too.

Xiao Ze, who was dedicated to the people and vowed to become a generation of Ming Jun, accidentally fell on a little lady.
The little lady was born beautiful and lovable.
So Xiao Ze accepted his life and got the name of fear.

ps:
①The male protagonist has no concubine, and he is dedicated to serving the country.

- Description from novelbuddy