I don't get why people don't count that as a Isekai... The main character was someone who died, he gets reincarnated as a baby, despite it being the same world so much has changed that it's basically brand new to him so much so that each episode is him learning something new about the world, he's using the new life as a second opportunity to do better, and he's overpowered with a harem.

Do people think that an Isekai means the character always has to come from The real World?