Secret Intimacy with My Mother-in-Law - A Carnal Work From Home Affair I Can't Tell My Wife About

The protagonist Junjiro was pessimistic and unhappy as a child because he was born with a weak body, but gradually regained happiness due to his best friend Yousuke who was always by his side and supporting him.
Shiori, who met them during school was also saved by Yousuke.
The three became good friends, but eventually Junjiro fell in love with Shiori. However Junjiro also noticed that Yousuke had feelings for Shiori too, and unable to control his own feelings, Junjiro told Yousuke how he felt and got him to help confess his love for Shiori and started dating.
As time passed, Junjiro and Shiori married and moved to the city. Junjiro eventually became concerned that he couldn't satisfy Shiori at night due to his physical weakness.
One day, Yousuke came to their city for work, and Junjiro who wanted to pay Yousuke back for his help in the past, forced him to stay with them rather than rent an appartment.
Afterwords, when Junjiro returned home from a business trip, the usually passive Shiori, shown him sexual skills that he had never seen before. Worried about why his wife suddenly changed after being left with their friend, on his next business trip, he set up hidden cameras in the house. However, nothing was shown on them and he became deeply ashamed that he suspected his wife and best friend.
But from there her mood and behavior seemed to change. Is it his imagination, or...

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.

I live together with my older brother and his beautiful wife, Miyuki. Living every day alongside such an alluring sister-in-law constantly leaves me aroused. One day, by chance, I discovered Miyuki’s secret. To make her mine, I used that secret to blackmail her.
The relationship that began with blackmail turned her into a slave to my desires, and while wearing the mask of “family,” we continued to pile up sins day after day, hidden from my brother’s knowledge…

With my mother "Shinobu", we are living a fulfilling life together.
She is reliable and has a stable income, so our life is not difficult. While I respect my mother, I also see her as a woman and find her attractive, but I suppress my lust as best as I can.
However, my mother is blind only to "that man". As soon as she sees him, she shows her womanly expression. When "that man" comes home, he holds my mother in his arms, regardless of whether I am there or not.
They show off like that as if to humiliate me, so my anger finally explodes, and in order to make "Shinobu" my own, I......