Games like Keiko-chan no Himitsu

If you finished Keiko-chan no Himitsu, the closest matches are Artificial Academy 2, Oppai Slider 2, 3D SexVilla 2: Ever-Lust, Twins of the Pasture and Delude - Succubus Prison. All 7 share its adventure genre and are ranked by how closely their themes and modes overlap.