I'm looking for mangas, where uke does blowjob to seme.

It can be:

1. Forced blowjob: seme is angry at uke and make him do it
   or
2. Uke is really horny
   or
3. Uke never does it before, but he changes his mind and he does it now

or
Seme is:

1. really enjoying it, it shows on his face
   or
2. seme has arrogant, cocky expression on his face

No
S&M relationship, where the seme humiliate uke.
Such scene where other men rapes uke (like in Animal X).

I don't like gangrape, but there can be rape but just where the seme rapes uke, no other men.

If you're beeing too specific you may encounter difficulties finding what you want. >.< I'll check, but I'm not sure I know this kind of yaoi, sadly.
Good luck

Variety's the very spice of life, That gives it all its flavor. -- William Cowper

Fine Play: uke does it willingly *and more by the same author.
Akiyama-kun: uke is really horny (it's a 69 if I remember right).
Kimi Wa Amai Amai... chapter 5-6: the seme forces him to do it.
Karada Meate de Warui ka first story: uke does it willingly but we don't get to see it.
Non Tea Room: uke is happy to do it, ahah.
≠ - Not Equal: he wants to do it but I'm not sure if he finished the job.
Koi Ja Nai Kedo (it's a sequel): uke is really reluctant but wants to satisfy the seme so does it anyway.

These are really just a few I can remember at the top of my head.
Also, if you take a look at Sadahiro Mika's works you'll find a tremendous amount of blow-jobs performed by ukes (be aware, there may be a lot of cheating too, but they always get together in the end).

It's the Art of Time, it's the Art of Life--
Of the player and the craftsman,
Of the writer of songs, of the creator of love,
Of those who will follow, of those who led,
There's no other way in the world ahead ♥

Ahh thanks a lot!! 🙂 I love the most when seme forces uke to blowjob 😛 😛

Akanai Tobira - the uke wants it
1-en no Otoko - they sort of switch roles