I’m disappointed this wasn’t what I initially thought, a Japanese boy deflowered by his vocal synthetizer :3
More simply (behold my Google and Wikipedia powers!), we’re with two vocal pack characters from the Vocaloid game, Rin and Len, who were created with the idea of offering the same voice, only sounding either male or female. So, the two characters having sex here are both non-humans, it’s less amusing ^^;;
There’s no scenario to mention, it’s good sex, simply. I must say, I was positively surprised by the drawing quality, nice, neat, no screwups, for a doujinshi this is top tier. Thanks to the scanlators behind it! Namely: Joseko, Lied, Time and Pincluc from Little White Butterflies
By the same artist, to this day, I also share Moetion Graphics (220 pictures), Miracle Magic Hour and Miku-san Ga 10 Shuunen Ni Iroiro Omoidashi Tari Suru Ohanashi.