This immensely popular h-series has been said to have changed the history of adult animation with it’s scenes of violence, perversion and lust, filled with hardcore sex and unusual sexual fetishes! It consists of three different anime titles each with their own series of releases; Isaku, Shisaku and Kisaku. They are named after the three sadistic brothers whom they are about.

What is an anime that is very close to reality?

It is probably easier to agree on which anime are unrealistic than to agree on the realistic ones.
That is so because each of us have our own definition of reality, our own unique way as to how we see the real world.
For example, someone living (or close to living) a hikikomori life may find Welcome to the NHK to be extremely realistic.
Others may find it to be less so. Having said that, the best way to find realistic anime would be to search by genre.
For example, the slice-of-life genre tends to have lots of candidates for the realistic tag. Anyway, apart from seconding Usagi Drop, Gin no Saji, Sakamichi no Apollon, I would like to mention these two: Tokyo Magnitude 8.0 They were trying to portray it as realistically as possible and I say they did a pretty good job. The series' setting is based upon the prediction that there is 70% or higher chance of an earthquake measuring 7.0 magnitude on the Richter Scale hitting Tokyo in the next 30 years, with the series illustrating the consequences of an 8.0 scale earthquake affecting the city. Bones stated that it would try to realistically depict the after-effects of such a situation and that it would collect and tabulate research on previous earthquakes and interview individuals who were affected by them. Byousoku 5 Centimeter The art is probably the best anime has to offer; it's so good that it almost feels real.
But, that is not why one would call it a realistic movie. [ Slight spoiler alert! ] Sometimes in real life, relationships and love just erodes away over time (and distance).
One moment a couple is deeply in love.
And then, life happens.
No happy ending, no forever after, not even a dramatic tragedy, things just die way with not so much as a whimper.
That is what's beautiful (and realistic) about the depiction of romance in this movie.