Tensei Kusushi wa Isekai wo Meguru is a Manga/Manhwa/Manhua in (English/Raw) language, Action series, english chapters have been translated and you can read them here. You are reading chapters on www.mgeko.cc fastest updating comic site. The Summary is

"Are you in need of drugs effective against villains?" Poisons, aphrodisiacs, wonder drugs, anything. Shin, a mysterious pharmacist whose origin is unknown to everyone, is creating miracles today too with the deluxe medicine he creates.