Based on the erotic simulation game by Dieselmine. 
 
The whole thing happened a while ago at a hot spring inn in a certain rural village... 
On a snowy day, an owner of an inn rescued a trapped fox. Months later, the fox's wounds healed and she felt a debt of gratitude to him. Her sincere want reached the god and the fox became a fox girl. The fox girl's olfactory sense enabled herself to visit the man's hot spring inn. There she found, however, that he was about to die at that time. Although he was approaching his last breath, he was only concerned with his hot spring inn that is in financial difficulties. While his consciousness was fading away, he asks the fox girl who appeared in front of him to rebuild his business. Then he died. Knowing nothing about business strategies, she started with searching for useful information in his room. As a result, she founds a know-how book of the hot spring inn management and a porn book themed on hot spring inn. The two books made the fox girl to think in a way that giving H services to customers will work out. 
 
(Source: DLsite English)

Based on the erotic game by 14rabbits.
 
After college graduation, Tanaka Daisuke started working and living alone. Even with the cheap, small, old, and untrustworthy boarding house ads, Tanaka-san immediately leaves his old boarding house. What makes him interested in these ads? If he pays the boarding house money on time, he will receive a special service from the Land Lady. What might that special service be? Having sex with the Land Lady with the small body of a child.
 
(Source: Translated and Edited from Nekopoi)

Based on the CG collection by TORYA!/Otona teikoku (TORYA!/オトナテイコク). 
 
It was a hot summer.
Out of work, the protagonist visited his family's house in the countryside.
His ambitions were in tatters. He forewent a job hunt in favor of lazing around the house.
That's how he got close with his brother's wife.
Her name was Arisa.
She was a stunningly beautiful Russian bride transplanted to Japan.
Her interest in Japanese was strong, and she was refreshingly open and tender.
It wasn't long before the bitter protagonist fantasized about stealing her.
Around the same time, his brother went on a trip.
The night before his brother left, he overheard that Arisa and his brother were in a basically sexless marriage.
What could be more perfect?
The protagonist had his brother beat in two departments: virility and perversion.
More than just making Arisa his own... could he get her to fall in love with him?
 
(Source: DLsite English)

Based on the erotic game by Grand Cru Bourgeois. 
 
Former Idol Utakata Ayuri threatened to be fired because the album is not sold much. Keita as her Manager tries to help her keep working in Idol world. However, Ayuri is easily desperate and attempts to commit suicide but is always thwarted by Keita. To be able to make a good song, Ayuri should have sex with Keita as usual. Can Ayuri finish the song? 
 
(Source: Nekopoi, translated)

Collaboration Works petit