Tensei Ojisan, Heroine ni Naru.

Ittetsu Wakigata—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! (Source: Flex Comix, translated)