The game is explicitly pornographic, with uncensored (or mosaic-removed) content depending on version/patches. It’s known for its high-quality fluid animation (using the “E-mote” system), full voice acting, and a relatively simple narrative about a male protagonist staying at a rural home with the two heroines. The “hot” you mention refers to the explicit sex scenes, which are the main focus.
Sisters: Natsu no Saigo no Hi – Ultra Edition Developer: Jellyfish Original Release: 2013 (Ultra Edition)
(Sisters: Last Day of Summer). While the original 2011 release by developer Jellyfish set a high bar for "active" visual novels, the is widely considered the definitive way to experience this sultry, sun-drenched mystery.