The dominant partner in a gay male on male romantic relationship in Japanese yaoi anime and manga, doujinshi and fanfiction. The seme is said to 'top' his uke. The seme is often (but not always) the older of the two/ more serious/ dark/ mysterious and more 'handsome' than 'cute'.
In the shonen-ai anime Gravitation, the mysterious Eiri Yuki is the seme over the pink-haired Shuichi Shindo.
In Sensitive Pornograph Sono Hanasaki has a seme (Seiji Yamada) a whole ten years younger than himself.