Onegai, Okaa-san tte Yonde! ~Gibo ni Naritai Onna to, Koibito ni Shitai Boku~

One day, the protagonist's father suddenly introduces a woman to him as his "new" mother-in-law from now on. He already knows too well that his father will change his partner again soon as that has always been the case until now. Therefore, he tries to behave like stranger to not get emotionally attached as much as possible. However, the moment he hears her voice and looks at her face, he realizes that he has fallen in love at first sight.