I remember the story but not the title. I'm looking for a yaoi oneshot or a doujin that was in an unspecified historical time in japan.

A ninja has heard a man who is potentially a danger to his master is in town. He comes to the man on behalf of his master and offers him tea. The man suspects it's poisonous and asks the ninja to drink it for him. He does, and returns to his master's home weakened. Insulted, he goes into the forest and demands a duel with the man, which the ninja lose. Then comes a sex scene in a body of water (a river?). When it was over, the man leaves the ninja with his dogs. He was pretty bruised up after that encounter.

Bump-

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 ♥

Is it Gakuran Ninpouchou
or
Otonosama Gorangyou
or
Urakatana Kaminoki second story?

No, sorry. The art style had some resemblance to IZUMI Yakumo/GD Mechano or IKE Reibun. The oneshot was on the rape-y side than romantic. It had an english translation, but wasn't in comedy nor school life(at least not a training ninja) category.

(Sorry for the late reply, went on vacation w/o wifi.)