Try the author nojiro guri’s work. Just search his name and all of his work will come up. I love all of his manga, you will fall in love with every story
Also
Tamayura
Life no senjou bokura
Revival blue
Contrast
Sayonara bokura
Reset
Neon sign amber
It's not all short manga, but I have a lot in this list:
https://www.mangago.zone/home/mangalist/2723961/
ao no tsubomi
okusama wa alpha
boku no high spec kareshi sama
I need recommendations those short 6 chapter Japanese yaois, I feel like I can only find super long ongoing Manhwas I just want a snack not a whole buffet