Straight guy Mike from the gym unexpectedly ends up with a dragon egg after a one-night stand. The child’s biological father — the dragon beast Rex — comes to take the baby away to follow the clan rule that 'bloodlines must not be left in the human world,' but he’s forced to stay and help raise the kid because the child recognizes him as its master. During the process of co-parenting, the two go from being at odds to sticking together, and the dormant dragon blood in Mike gradually awakens due to their emotional bond. The surge in his dragon blood is mistakenly seen as 'usurpation of lineage,' bringing a hunt from the main dragon clan. The trio is forced to fight together. In the climax, Mike fully transforms into his dragon form for the first time, showing the mark that only the rightful royal bloodline possesses — the pursuers finally realize that the 'threat' they were ordered to eliminate is actually the long-lost prince they thought had died years ago. Everyone switches sides, and the conspiracy of the usurper who orchestrated everything is exposed.
