Slow Sex: Jibun Shijou Saikou H-keikaku

Torako Kisaragi, the director of Girl's Clinic, offers women sex-related advice in a straightforward and hands-on manner. Don't leave sex to men. If you improve yourself, your sex life will definitely improve, too!

(Source: Kodansha, translated)

Note: Also includes the one-shot story Koukou Kyoushi