Seikyouiku no Jikan desu

"I want you to teach me how to make men ejaculate!" As she says that, my old homeroom teacher squeezes my hand... Yohei Nishiyama is a college student who was working part-time at a video booth that's about to go out of business, when a mysterious beauty who looks completely out of place appears before him! Looking at her face when she's trying to rent pretty hard-core porno, Yohei feels like he's seen her face before... And of course, it turns out that she was his old homeroom teacher, Ms. Yuri! She should've gotten married half a year ago. What in the world is she doing here!? Yuri reveals her private life to him... and from that day, the two get stuck in an immoral relationship...!
(Source: Coolmic)
Note: Split into 42 episodes on mobile reading platforms.