Based on the game by TinkerBell.

Saeko is introduced to an online sex shop by her co-worker, Sayaka. Curiosity gets the best of her and she orders herself a small vibrator. After discovering the pleasures the sex toys bring her, she gets addicted to masturbation and finds herself doing it all the time. Soon enough, Sayaka joins her in her sex escapades and things start to escalate to new heights.

(Source: AniDB)