20/01/2021:
What I understood so far: Real prince Daniel helps isekaied boy Rael and they switch places between a mercenary guild or something and the palace. Another prince (emporor) visits their kingdom, falls in love with Rael on the spot. He spends the next months with Daniel after Rael got enough of it. Then new prince (emperor) has to leave, and being in love; he requests to be allowed to fuck the prince for one night and promises good trade relations as an award. Rael panics and Daniel offers to take his place. Rael is okay with whoring himself out because Daniel saved him. Rael and other prince (emperor) fuck for three days. Prince (emperor) leaves and something happens one year later...
Shadow crown