main character is a strong, independent, brilliant woman. She isn't abrasive or obnoxious, just confident in who she is. Her success in the story is entirely from her own efforts.
love interest is a well rounded character, not an Everyman stand in. His own strengths and weaknesses are plot relevant and he grows independently of the mc.
the romance progresses at a steady pace and isn't a will they/won't they for two seasons.
romance is one of many plot lines, not the only one. It's also slice of life and medieval politics.
and of course, everyone's adults. Everyone has normal body proportions and healthy personalities.
Seinen and Josei are genres targeted at young adult men and women respectively. They both tend to be more realistic and actually mature in their writing, as in having complex character motivations, realistic toxic relationship problems, etc.