All I remember was being interested in the summary, and then forgetting to save it for later 🙁

I believe it was a summary about a poor boy telling off his father for divorcing his mom, and then confronting his dad's new son (step-brother). Years pass, and he's now a teacher but one day he's confronted by the now older, and good-looking step-brother who comes demanding money and sexual favors from him after learning something about him that can be used for blackmail.

I hope this rings a bell for anyone

Tsume to Toge?