Read "Kimi no Okaasan wo Boku ni Kudasai!" if you're looking for a good story about a younger guy, who is still an adult, having romantic interest in an older woman.
That story has a couple that genuinely care for eachother and support eachother through hard situations. The male lead is learning emotional maturity and how to be the kind of person who can make the woman he loves, and her son, happy. The female lead is learning how to rely on others again and not having to shoulder the burdens of her life all on her own.