Having finished the main series of Sweat and Soap, the creator got permission from the publisher to self-publish this explicit bonus scene where Asako and Kotaro have decided to try for a baby and have sex for the first time without any birth control. So they make whoopee. There's a little bit of a specific sexual fetish that is consistent with the characters, but mostly its just wall to wall bonking.

I was able to find the book for purchase and download at the site below. With a 300 yen coupon for a new customer sign up, the book was discounted to 30 yen, or about 30 cents. Pretty good for a 24 page story with some extras.

https://www.dlsite.com/girls/work/=/product_id/RJ328113.html ( )