It's not uncommon for children's shows to include a bit of adult humor. However, a scene in Yu-Gi-Oh! VRAINS Episode 4 goes beyond what most shows would even dare attempt.
The scene involves two robotic characters, Ignis and Roboppy. Roboppy is a small, toy-like robot that acts as a maid in main protagonist Yusaku's home. Ignis is one of several AI that was developed by Dr. Kogami, a scientist who had kidnapped Yusaku and five other children, forcing them to duel to collect data to create these AI. This particular Ignis is called the "Dark Ignis," as each one represents some sort of element like "Aqua" or "Windy." However, Dark Ignis was reduced to only his eye after attempting to rescue the other Ignis from the Knights of Hanoi.
The two are shown under a bed, where Ignis says things like "more to the right" and "don't!" It's very clearly meant to imply an erotic moment, with the wording and moaning. The two seem fearful of getting caught when they hear someone coming towards the bedroom, so they panic. This isn't a one-time deal, either. It's referenced at least twice in future episodes.
The biggest question among the comments of the YouTube clip seems to be "How would 4Kids get around this moment?" 4Kids was notorious for their censorship of anime, particularly scenes that they deemed inappropriate to children, despite other shows and channels allowing that same content. Yu-Gi-Oh! has seen its fair share of censorship by the company, from guns being taken out of scenes completely, making it look like the wielders are just pointing at Kaiba to a punch from Joey being cut so that Atem just ends up on the ground for no reason.
Japanese censorship laws are very different from America's, with anime being allowed to depict breasts and cleavage without being altered in any way. While shows for smaller children tend to be more family-friendly, shows like Crayon Shinchan are notorious for showing bare bums and private parts. This is surprising considering that the country pixelates the genitals in porn. However, anime seems to be an exception to Japanese anti-obscenity laws.
While most anime and manga is self-censored by the creators, there seems to be a general understanding of what is and isn't obscene material. It seems that robotic eroticism is the latter.
