Kakushite! Makina-san!!

This risque romantic comedy story centers on Eita, an introvert mecha otaku high schooler who has a crush on the school's most popular girl Makina. When Eita finds Makina at her doorstep, he is flustered, and even more so when Makina reveals her secret: that she is a "sexaroid" robot designed for pleasure, and she is asking Eita to conduct some repairs on her discreetly. While Makina immediately tries to make a move on Eita physically, Eita struggles to contain himself, while also hiding her secret.
(Source: Anime News Network, edited)