Kore wa Sex ja Arimasen

A college student living alone, Suzu Tachibana's hobby is playing with sex toys. One day, his secret is revealed to Kamiya, a handsome but surly-looking man who lives next door, because of a shipment mix-up. Kamiya nonchalantly claims that he is the one who developed the sex toy, and offers Suzu a proposal. In exchange for providing Suzu with new toys, Suzu would give feedback to Kamiya about his impressions of the toys in real life.
(Source: Ichijin Plus, translated)
Note: Includes an extra chapter.