Shirokuro ~Shikijoushou no Osananajimi o Sewasuru Koto ni Natta, Kanojo ni Naisho de~

You - Minagawa Tooru - are just a regular student with a bit of an otaku side. About a year ago, you started dating your girlfriend Nagisaku Shiro, who absolutely adores you, and you've been enjoying a cheerful school life together.

One day, when you thought this happy routine would go on forever, you suddenly got a request from your childhood friend Chouno Kuro, whom you had grown distant from over the years. She asked you out of the blue to have sex with her. Kuro, who is a year younger than you, was your first love, someone you had been close to since childhood. Your friendship drifted apart after she rejected your confession.

Now, seeing her naked body, her heated breaths, and her pleading gaze made you feel a rush of emotions. Despite having Shiro as your girlfriend, you couldn’t resist that sweet temptation and ended up sleeping with Kuro. Afterward, Kuro confessed that she had become a recluse due to developing a hypersexuality after being molested. You were the only one she confided in; she hadn’t even told her parents about what happened to her.

To help Kuro achieve her wish of overcoming her condition and being able to go back to school, you decided to support her. Kuro, struggling with her hypersexuality, gets aroused in public if she doesn’t release her urges through sex. You found yourself in a position where you had to keep having sexual encounters with her, like handling a ticking time bomb.

But you also have your adorable girlfriend Shiro, who cherishes you and always greets you with a bright smile. So, to keep Shiro’s smile from fading, you decided to take care of Kuro in secret.