GVH-628 — My Girlfriend's Sister Teaches Ejaculation Technique, and I Keep Failing the Lesson by Cumming

Ayaka, the protagonist's girlfriend's adult sister, secretly works as a technique instructor for porn actresses and sex-industry professionals. When the scheduled male model cancels, he fills in, hidden beneath a sheet with only his blindfolded cock exposed. Ayaka's expert hands make him fire repeatedly, and her students keep teasing his oversensitive cock after every ejaculation, turning the lesson into one premature finish after another.