2 needed to calculate an average
Fifteen-year-old Marion is intelligent, handsome and loved by everyone at his French boarding school, but the boy holds nothing but disdain for both his classmates, and himself. For Marion is devoted to rationalism, believing that emotions such as anger and love are unnecessary – even sex is merely a means of ensuring a species' survival. But deep down, this attitude is simply a façade that was carefully constructed to protect Marion's naivety and fragile emotions, and when a chance encounter brings a seductive adult woman into his life, even he won't be able to retain his icy exterior…
Both these manga are short, female-oriented stories about May-December romances. They don't have many similarities besides that, but the subject is fairly rare in manga, so check out both if you're interested in cougars and their much younger suitors.
Gorgeous 70s-era shoujo dripping with melodrama, forbidden love, and beautiful tragedy. If you're into this genre (and if you're reading this you probably are) then I highly recommend reading both of these.