I see, um, so this is basically a glorification of pedophilic molestation.
For those of you who are unclear, the issue with having sex with children is that they are incapable of giving informed consent. So even when these prepubescent twin boys are begging for Arata to show them "skin to skin loving" and even when they get jealous whenever the other twin is getting more of Arata's attention than them and beg him to focus on them, that doesn't mean that they are giving consent. The words coming out of their mouths are technically giving Arata the go-ahead, but those words are no different than if a drunk person gave someone the go-ahead--they're not actual consent. And the fact that none of the sexual experimentation in this manga is portrayed as Arata taking advantage of these children, but instead is portrayed as him showing them the ropes, is what makes this a glorification of molestation.
However, the art is okay and the sex scenes are pretty steamy, so I guess this manga has that going for it. But that also means that it's just a shallow piece of smut, making use of taboo sexuality to make it more exciting. It's not a good story. It doesn't have good characters. It has no value and on top of that, the way it thoughtlessly portrays "consent" could actually be harmful if it made pedophile readers feel that it's okay to act on their impulses (as long as they got the "go-ahead"). If you wish to read it for the smut, at the very least read it thoughtfully.