[Sanada] Zubo Zubo Ero Apuri 18 ~suppon supon oyayubi hime kyushutsu sakusen~

A teacher's mysterious smartphone app shrinks schoolgirl Rika into a helpless thumb-sized plaything, and he wastes no time putting her tiny squirming body to work until she faints from the overstimulation. But classmate Ayase knows exactly what he's been up to—and with photographic evidence of his night with the shrunken girl and a threat to ruin him, she drags him to a park toilet to service them both. What begins as one man's secret fantasy ends with Tani-sensei becoming a slave to two demons of his own making.