Based on your description, it sounds like you are looking for a story summary or a narrative piece based on the anime/manga title "Ore no Yubi de Midarero: Heitongata no Kanojo" (officially localized as Fascinated by My Fingers or Messing with My Fingers), specifically focusing on a scenario in a salon after closing time.
“Then I won’t.”
The Romance: He begins to use his skilled "hairdresser's fingers" to caress her, initiating an erotic romance between the mentor and his assistant. Characters
“We have all night,” he said, and his fingers finally, finally slipped beneath the fabric, warm against her bare skin. “And I’m going to make you lose your mind. Just with these.”
Ore no Yubi de Midarero (translated as Crazy Over His Fingers