Yabai! Fukushuu Yami Site

Both includes the girls kidnapped and brutally raped with sad ending, maybe. It depends on your perspective. 

Series of kidnapping, abusing and torturing the heroine. Both might will made you felt uneasy and disturbing. 

Both protagonists rape a girls out of revenge and they gotten away with it. 

They both have a lot of bondage and neither one is for the weak hearted. If you like rough, bloody, kinky sex then you will enjoy both of these shows. 

- The protagonist's sister is being bullied by some hot chick - The male protagonist decided to take revenge unto those who bully his little/big sister 

Both are hentai about a guy who holds girls in captivity. Both feature bondage, but Bondage Game is way more extreme. 

Both deal with a guy seeking revenge for his family so he goes for the one responsible and does what every hentai does with revenge kidnapping, humiliating, and molesting.