[TDTK (Kawasaki Tadataka)] "Kanbai Shimashita" [Chinese] [鬼畜王汉化组] [Digital]

The story is about this 2 classmate, the girl is an author, and the boy is a comic artist. So that guy found out about the girl's identity as an author and proposed to work together and create a doujin to sell in the next comic con. But the result is that they only sold 3 books out of the 800 copies they printed and they were depressed AF. The sex scenes we see in page 14~15, and 22~25 happened before the comic con, the boy said he is facing problem with the drawing and asked her for help... and then seggs!!!! So after the comic con ended, and they were depressed AF, the boy argued with her a bit and fucked her raw because she promised him she would let him do it raw after the comic con ended. In the ending, they are planning for the next comic con event showing they have not given up yet (it's a cute and wholesome end)

it is not his sister, it is his classmate