Zenos has come far from his origins as a slum rat--but all that comes to an end as the adventurer party he's been traveling with kicks him out. With no official healer's credentials, he can't work normally, and no other party will take him now that he's been so obviously expelled. So it's back to the slums. But Zenos has underestimated how much power he's accumulated with his nonstandard spells . . .
This is pretty much what you would expect from yet another "kicked out of the party who didn't realize I was so overpowered" story. Zenos takes the opportunity to reevaluate his life, finally clues in to the fact that he's been used pretty badly, and decides he'll start his own business in the slums, but this time he'll make sure to get paid for any work he performs.
This leads to him accidentally taking over as he doctors his way through the three factions that compete for the slums. Since everybody now owes him (and the three faction leaders have, of course, fallen in love with him), things are actually getting better for their home. Of course, the nobility starts hearing rumors of what's happening and decides to investigate . . .
I may or may not keep following this one---it depends on how annoying the harem aspects get. We have the ghost who haunts the house where Zenos chose to live, the underage slave girl he bought, the three faction leaders, and the noble who came to investigate. I do like Zenos's unorthodox, self-created magic, but right now it's about 50-50 plot versus harem. But the first volume is decent. I rate this book Recommended.