Oji-san ga Joshi●sei ni Warui Koto wo Oshieru hanashi

Oji-san ga Joshi●sei ni Warui Koto wo Oshieru hanashi manga summary: "I'll teach you what's bad." As a high schooler, Ayumu's at a sensitive period in her life. She ends up being educated on adult matters by a bearded old man wearing a black t-shirt