Drugstore in Another World: The Slow Life of a Cheat Pharmacist (Manga) Vol. 8 (manga)

Coveting the power of Reiji's potions for himself, the king of all demons suddenly appears at Kirio Drugs, demanding free merchandise! As it turns out, the demon king is broke, and pretty soon he winds up accepting a job as the pharmacy's newest staff member. He's also head over heels in love with Noela, and plans to get his hands on a forbidden potion that just might make his romantic dreams come true. The lazy days at Reiji's pharmacy are bound to get livelier with the Lord of Fear on the payroll!