I am looking for a manga I read ages ago !!

the story begins with the main character being model for his sister or his sisters friend and then one thing leads to another and they have sex then in next chapter his classmate walks in on them or something and then he starts having love relationship with his classmate and in later chapter his friend starts sleeping with his sister and stuff i don't remember to well bet the art was similar to super taboo really simple and stuff so if someone knows the name please tell me