ハッピー・ハーレム・スクリプト～こんなにHな女の子が実在するワケがない！～

The protagonist, Masaki, is an aspiring writer. Suddenly, he finds himself boarding at a relative's house, running a small restaurant together with his younger sister Ayano, a few days after the move.

Recently, he received a job offer to write erotic novels, but things are not going as smoothly as he hoped. The pressure from his editor, Kayo, to deliver the work is intense, and he is mentally and emotionally drained.

One day, Ayano, unable to bear seeing her brother in distress, speaks up.

"Shall I help you out?"

Driven by the pursuit of authenticity in his writing and fueled by his own desires, Masaki accepts Ayano's proposal and becomes involved with her. This leads to even closer relationships with the sisters from their relative's household.