The manga is about 2 classmates, but then the cute guy suddenly becomes a girl. Then confessed to the other and I think he tried to seduced him. When the other finally gives in, the cute guy cried since he already became a boy again, but the other guy didn't care anymore.
Now i also want to know
YES IT IS! THANK YOU!
They're side couple. The uke's name is sasame, I think? The seme is i think a tattoo artist that has a shades. The only screenshot I have is when the seme hit the uke with the door as he opened it.
Regarding the main couple I think one of them is also a tattoo artist.