This is a virtual world type of isekai, but it's so badly explained. It tries to be practical and says that it was developed by the government, run on servers and NPCs have limited intelligence and whatnot, but the most glaring is this -- MC entered the virtual world by entering a http address and getting sucked into his computer screen. What? And yet, at this world seemingly created by a hybrid of magic and science, nobody bats an eye at this insane technology, nobody seems impressed by the world they were transported to, or questioned whether they would be able to go back.
So, yeah, badly explained world and characters that don't act according to common sense.
he has one and only one partner, and in exchange for the cliched pattern of collecting harem members like pokemon, their relationship grows and builds gradually to a mature one, physically and emotionally. I found it very satisfying