Title: Delinquent Omega Belongs to the Beast King!
Rintaro is a delinquent in a city that is steadily being overrun by crime. He has a unique sense of justice, trying to clean up his home even while being on the wrong side of the tracks himself. While fighting off some muggers going after a fortune teller, Rintaro picks up a strange mirror reflecting the image of a fantasy kingdom he's never seen before. Just as he's about to ask the fortune teller what he's seeing, the mirror sucks him inside, transporting him to the very fantasy land that it depicted.
Once there, he's faced with a scenario not all that different from the one he left behind. A man is bound and being robbed while two criminals shake him down for all he's worth. Rintaro isn't going to just let this slide, so he does what he always does: dispensing justice with his fists. He has no problem doing so until his body suddenly revolts against him. As it turns out, in this new world, there are different genders: alphas and omegas, and Rintaro happens to be an omega. Before the criminals take him, the man bound on the ground frees himself and picks up where Rintaro left off, saving Rintaro.
Rintaro is beyond thankful for the man, but it's hard to be thankful for long when Varuna, the man in question, turns out to be the lord of the land, and he believes Rintaro is his fated mate. Rintaro's new body is all too happy to go along with Varuna's stimulation, but Rintaro's mind isn't ready to accept it just yet. Can Rintaro learn to accept his new role in this world, or will he run away to try and forge a new path?