Kagaku na Yatsura
A "science trouble" romantic comedy OVA bundled with the manga's fourth volume. It follows a high school boy named Komaba Haruki and his two girl friends: the cyborg girl Airi, and the half-dog girl Ayana. The two go to extremes with the power of science, which only gets Haruki involved in ecchi troubles.
(Source: ANN, MAL news)