Oni Chichi

Similar animation, character design. Different in that Oni Chichi is about the father approaching the girls while Papa Love is the other way around.  

You see those covers? You can not say they're not similar, at least talking about the main girl, in the actual animation of the OVA of Manin Densha the artstyle it's not the same, so it stops being so similar, but the main character details are still there, blonde, two side tails and highschool girls, there's also the fact that in both there's rape involved, if you like that both are recommended. 

In Oni Chichi there's the incest aspect, but it's in a way about a teacher fiddling with his students, in fact two of those students and the ones who get almost all the scenes are reminiscent of the ones found in Boin, at least in terms of character design (one is blonde, the other with short red/pink hair and both with big breasts). If you like the idea of a sensei with the protagonist role in a hentai, go for any of these. 

Both Female MC are a tsundere blonde, got raped by MC then slowly fall in love with him. They both like to curse the MC when they do the deed. 

The Crossover felt great. Airi is from here and the animation is Same since the both shows are from the same studio 

A happy life, you can say "normal", can live by your work or school, trusting that you will not spend anything wrong. Unless you're a girl and the main character of a hentai. Two OVAS playing with the emotions of the girls, through drug use, which make them objects massive perversion of those closest to her, either at work or at home, their very existence is for fill the pleasure of someone else. 

These two hentai both have three-way relationships between an older guy and two school girls. Both are made by Poro so they have very similar animation. Oni Chichi involves father/daughter relationships, while Floating Material has teacher/student relationships. Oni Chichi has less consensual sex than Floating Material. 

Similar characters, similar story. 

Another one by Poro involving father/daughter incest and rape in a high school theme. Art animation are very similar. 

For people, who were so excited by ecchi-only lolicon in Kodomo no Jikan and lawful Main Hero, but wanna some more explicit content, there is a Oni Chichi, in which the teacher too learning horny girls around him... With his love stick! 

Well, the only thing similar are the girls... a black-haired sister and blonde sister with twintails. I highly recommend Oni Chichi Re-born too since it contains no blackmailing and develops the premise quite well. Overall both are quite enjoyable hentai series.