I’m the Heroine’s Sister in an Erotic Game?

A certain man, who was diagnosed with cancer, finally died peacefully...but when he next opened his eyes, he found himself in the world of an erotic game. In addition, he also got thrown into the body of the sister of one of the heroines! What awaits him? He doesn't even know the plot of this world--he did not even have time to go through a few episodes. What adventures await him in this new body? Note: The picture is not mine. — Description from novelcodex.org