Adult PC Game: Dark Hunter Kuro Ver.1.10 by PIEROCK GAMES Archive

One day, Tachio, an ordinary office worker, is suddenly transported to another world overrun with dark monsters known as Yamimon. In this strange world, he is attacked by Yamimon, but is saved by the beautiful dark hunter Kurenai, with striking red hair and large breasts.
However, the moment he comes into contact with Kurenai, he fuses with her special battle suit, Gear.
Thus, Tachio fights alongside her as her suit during battles, while searching for a way to return to his original world (while being made to take care of everyday things at home).​