http://www.mangago.zone/read-manga/gosan_no_heart/
Unexpectedly carnivorous..., like this?
http://www.mangago.zone/read-manga/koi_wa_itsumo_arashi_no_youni/
umm promiscuous as in playboy uke? i don't have them tho but if you like i had a collection of uke who loved sex but most are pretty much committed to their partner when they started going out. http://www.mangago.zone/people/tag/49344/lewd+uke/
also, the seme that you described had me remember these guys
a traditional and straighlaced japanese man but transforms into an insatiable wolf when worked up http://www.mangago.zone/read-manga/memory_of_the_future/
a gently cry-baby younger seme but gets aggressive and hunky in bed http://www.mangago.zone/read-manga/ichiban_chikaku_de_koi_o_suru/
'notice-me-sempai' type http://www.mangago.zone/read-manga/sweet_chapel/mh/c001/
Looking for yaois with promiscuous ukes who fall hard for their seme! The semes are preferably the more indifferent type who only get wild in bed. ლ(´ڡ`ლ)
Ooh, and I'd love other yaois with unexpectedly carnivorous semes! Like:
http://www.mangago.zone/read-manga/koisuru_barairo_tenchou/
(≧∀≦)