Greetings, greetings~
A significant quantity of phone otoge are in the "childish" zone, but I usually do not take most of them too seriously in the first place. There aren't really many that are necessarily erotic, and translated otome games are still relatively new things. Many will often get to the bed scenes and just skip over, or the more explicit scenes are contained in the spin-offs. Hah. But from what I remember people saying before (urg, it is taking a long time to find the title), "Shall We Date?: Can't Say No" has the most kinky stuff to read. Haven't read it myself, but that surely means details.
I played Man with a Pearl Earring, as well, and that ending... =w= But I still overall liked the introspection. All of Koyonplete's novelizations (really, they are only as long as very short stories to be read in an afternoon) stuffed in a visual novel format seem to contain the mature stuff.
Yeah, PC stuff has more to offer. If you are fine with Japanese stuff, there are things like the S&M action in Diabolik Lovers, Ijiwaru My Master, etc.. You can also find some OEL works here and there with more mature content, and there are many groups still in progress that definitely have that smut.
Are you... about 40 years old? JKJKJK... unless you are.