The Infamous Yaoi P-List 1 (WARNING: Hardcore kink ahead!)

Catheterization with peeing, peeing during sex (uke)
Mild BDSM

Uke wants to try BDSM and has seme catheterize him among other things. Seme has sex with uke with catheter and vibrator still in anus (double penetration).

[Note: semen can only exit around the outside of an inserted catheter, so any liquid that flows out of the tube itself is coming from the bladder]

Ch. 1 - Catheterization, urethral stimulation
BDSM
Rape


Seme restrains and catheterizes uke as punishment using it to stimulate the uke's urethra while licking the head of the uke's penis at the same time.

Ch. 27 - Urolagnia, voyeurism

Kidnapper becomes aroused while watching his captive pee into a toilet.

Peeing during sex (seme- in uke's ass)
Characters with animal characteristics

Animal-eared seme pees inside of animal-eared uke during sex to mark him as his own.

Ch. 5 - Peeing during sex (seme- in uke's ass)

Two men have sex in the office after hours. On impulse, after coming inside the uke, the seme pees inside the him and tells him not to let it spill out. Thrilled that his partner showed such a cute, kinky side, the uke asks him to go out with him.

Ch. 5 - Peeing during sex (uke)
BDSM

Shintani has some rather intense, rough sex with Sudou. When Shintani pulls on Sudou's nipple rings, Sudou pees uncontrollably.

Ch. 1 - Catheterization, urethral stimulation

Seme inserts a catheter into a masochistic uke's urethra for the purpose of causing him erotic pain. He tells him he will insert a thicker one once the uke gets used to it.

Ch. 2 - Catheterization with injection of fluid into bladder, omorashi- naked wetting (not pee)
BDSM

Seme injects fluid via catheter into uke's bladder. Uke shoots fluid from penis during orgasm.

Ch. 1 - Desperation, omorashi- wetting with pants pulled down
BDSM

Uke pees while being spanked.

Peeing during sex (uke)

In a A/B/O universe, Levi is an alpha who cannot impregnate anyone, but responds like an omega. Eren is an omega, but penetrates Levi because he enjoys it. Levi leaks pee during some very hot car sex.

★ Special thanks to TooDeepInThisShit for the recommendation

Ch. 2 - Peeing during sex (uke), urolagnia, voyeurism

Seme watches a sex video he taped of his sexually excited uke peeing himself during sex.

Ch. 7 - Catheterization with peeing, desperation, urethral stimulation

Seme catheterizes uke at a hot spring and makes him pee through it to avoid dirtying the water, then stimulates uke with the catheter