Reincarnated Old Man becomes a Heroine manga, Tensei Ojisan Heroine ni Naru, 転生おじさん、ヒロインになる。 Wakigata 

Ittetsu- A straight forward, family man who has worked for more than 23 years as a company employee. His job title is general manager but in his off time, he likes reading manga——? This salaryman who was living a mediocre yet happy life, got reincarnated into the world of a Shoujo Manga. “How did I end up in this place as a high school girl?”
“My beloved family must be waiting for me!” Cheer on this reincarnated Uncle as you read this story ripe with love and laughter!