Stealing My Brother's Wife - The Lewd Secret of My Sister-in-Law, Melted by My Blackmail

This work tells the story of the protagonist’s wife and her younger sister, who get a job at a gym and gradually fall into depravity.

During the summer vacation when his parents are away, he begins living with his step-sister.

Ishidou Narumi, a student attending a rural all-boys' school, spends his noisy but enjoyable days with his slightly ditzy best friends.
He has a "secret" that he has not made public.

In this all-male school is a popular, gentle health teacher named Mitama, who seems to be the human embodiment of healing.

Another one is Aya, his homeroom and chemistry teacher, who is feared because of her sharp eyes and strict attitude, but is also popular because of her model-like appearance.

As the only ladies in a school with no female students, these two women and Narumi have a "special" relationship that they do not tell anyone about.

Although they act respectable at the school, it's all just a facade. The truth is that one is a spoiled, no-good Oneesan, and the other is a timid worrywart born with a bad look in her eyes. Since he happened to know those sides of the girls, Narumi has developed a particularly close relationship with them.

However, they were still teachers and student. No matter how close they were, there was a line they would never cross. But the situation changes drastically when an enfant terrible named "Patricia" enters the picture.

Patricia (aka "Patty"), arriving as an English teacher, falls in love at first sight with Narumi after a certain incident. Being a bundle of energy, Patty quickly makes a move on Narumi (in a naughty way)...
From there, his relationship with Mitama and Aya begins to change.

Who will win this sudden battle?

Mitama, the pampered Oneesan?
Aya, with the face of a wolf but the heart of a rabbit?
Or Patty, rushing headlong into everything like a wild boar?

It all depends on Narumi's lower half...?

Rick used to be a Knight and was fighting for his country for years until finally losing the war which also results in losing the country to another.

Queen Sofia is wife of the current King and always worried about not being able to bear a child even after 15 years of marriage.

As the successor problem arises, the King has to welcome a new concubine and it saddens Queen Sofia to the utmost.

As prisoner of war, Rick is disowned by his own family after being released and disarmed.

While thinking about his vague future ahead, Rick meets Tanya, the maid who used to serve his family before becoming personal maid of Queen Sofia.

Tanya reveals that Rick is descendant of former King and gives him the duty to impregnate the Queen as it's necessary to preserve the old King's bloodline.

Our heroine, Uemura Airi, has pledged her future to her older boyfriend, Makihara Shingo.
Meanwhile, she begins a relationship with her boyfriend's younger brother, Shinji.
A master-servant relationship is developed... Airi is the master, and Shinji is the servant.
And so the story of a female who seduces a male unfolds.