JKと淫行教師5～借金姉妹編～

The protagonist is a Japanese history teacher at a private school.
One day, he gets a call from his uncle, who happens to be a loan shark.
Apparently, the parents of two famously beautiful sisters—students at the school—have gone bankrupt.
The uncle suggests sending the girls into the sex trade to pay off their massive debt. Hearing this, the protagonist hatches a plan.

“I’ll take on that debt for you. But in exchange…”