Like in Uchi no Darling Eikoku Shinshi, where the uke grown up, educated and stuff, but has no idea what sexuality is, so when the seme comes along, he's kind of oblivious.
Thanks 😀

By oblivious uke, you mean like... a virgin uke who doesn't know what to do? Or a uke who is all innocent and keeps asking himself "omg, what's this feeling"? Or just a uke who gets all soft and dreamy while having sex?

Jun from Koibitogokoro is really innocent and new to sex. Kakeru from Hohoemi no Nichijou doesn't even know how to masturbate... Misato from Junketsu Drop doesn't know a lot about sex either. Youichi from Hana wa Saku ka also doesn't know a lot about relationships (yes, it's yaoi, vol.4 for more details). Masami from Renai Kyoutei Nukegake Nashi! is a virgin and gets all dreamy just from a kiss (it has blackmail... kinda).

If you tell more about what you want, I can list some more.