A greater Outer God of change comes to Earth and starts an apocalypse because of which Jihan and his allies decide that making Jihan into a God is the way to go, he does it, becomes the god of Rules, Results and Games and makes 9 Towers in which all the Monsters from portals leading to other worlds go as well as all Abyss monsters (and supernatural creatures of the supernatural world), meanwhile a System becomes available worldwide to everyone and it pretty much turns into a korean system apocalypse, Towers in which people get loot, Rankers, Guilds and even Constellations which are likely the powerful supernaturals which were already present pre-system apocalypse.
That all is shown after a three year time-skip and only then does Jihan get home to find his mother there, even though he apparently couldn't find her for those three years, and she just drops that her husband, JIhans father is some dimension traveling problem solving warrior and she, a dragon, fell in love with him, which led to Jihan, who was however a normal human child when born.
Also the martial arts girl decides she has to go on an adventure for some items to solve an imbalance, his other allies have likewise either parted with him or gone to explore other worlds. Only green boy friend his item (the heavenly sword now bound to him), remains by his side and they're kinda inseperable due to magic immortal shenanigans.
It has a certain logic to it, with the system apocalypse and everything, but a lot of it is rushed and a lot of plot threads feel left open, the author seems to have pretty bad health and that's their excuse, although they said they were planning a new series already.