Hika Ryojoku: The lust of shame  

悲花陵辱~罠にはまった義兄妹(ふたり)~ 

Shinichi and Megumi aren't exactly blood relatives. When their parents decide to marry, they find themselves pushed together and having to work the oddities out of the situation. Fortunately, they eventually learn to love and respect each other. However, their idyllic life will soon turn into a nightmare of lust and debauchery!

Two thugs at school take a liking to tormenting Shinichi. As things start to get out of hand, their attention is turned to his innocent and defenseless stepsister... and the nightmare of lust and depravity starts to unfold... Will Shinichi be able to keep them away from her, or is that asking too much?