Kyou Kara Tsukaeru Isekai Renai Manual

Just as Haruchika Isezaki was confessing to his first love, he is suddenly summoned to another world. His summoner, the goddess Clementine, gives him an unusual mission: to make seven girls, destined to become the mothers of the next generation of heroes, fall in love again. These girls have lost their ability to love due to a curse cast by the Demon Lord. In other words, Haruchika must convince them all to fall in love with him! To return to his world and hear the answer to his confession, Haruchika accepts this mission and sets out to save another world through love. Having mastered the art of romance through his study of female psychology, his journey to fulfill their first loves begins — a romantic tale about saving another world through the power of love! (Source: Nico Nico Seiga, translated)