Fantasion is an older game from back in 2010 made by developer Yukijirushi Nyugyou, featuring the kink of a small male vs. much larger female characters; a theme in several of the artist’s works. There are several platforming based levels that sport a very simplistic, yet appealing art style. The CG art, while perhaps not the artist’s best work, is pretty decent as well. Here, I play through the first two stages. If you beat the game, you are presented with a code that allows you to play as the game’s final boss, although there can be no sexual interaction with any enemy while you play as her, unfortunately.
If you care to, give this game a try: http://www.dlsite.com/ecchi-eng/dlaf/=/link/work/aid/daffiliate/id/RE071653