any type of seme like Ken-san?

My recommendation would be kokoro. It is a really sweet story, with an age gap of 17 years. But stil so kawaii! (︶︿︶)＝凸
(Soory for spelling mistakes tho)
http://www.mangago.zone/read-manga/kokoro_kanda_neko/

already read it,

Super late :3 but you should check out this list. I also love age gap

http://www.mangago.zone/tag/Age%20gap/