Why there is only a single manga with male lead? This manga incorporates guilt and regret intertwined into a plot with an older man falling for a younger girl.
Good romance mangas with older female leads? : manga
Almost all were shoujo, sadly, sorry but im not a fan of girl stories even if i have a couple that i really like since the atmosphere, premise, outcome, drama is not to my liking.
There is a continuous theme of love having no bounds since there is a large age gap between Niina and Atsurou as she was born after Chitose died when Atsurou was 14.