Mushoku Tensei: Jobless Reincarnation

[Ryllharu]

Keep in mind though that this series is considered one of the progenitors of the modern isekai genre. It's been around as long as Re:Zero has.

That's not an excuse, and it is also a completely invalid explanation. Shield Hero started at nearly the exact same time. Harem in the Labyrinth of Another World predates Mushoku Tensei by years.

They're all Shōsetsuka ni Narō series. Plenty of other "Imma Raise a Slave" manga started at similar timelines. Himekishi ga Classmate also started around the same time. By the time Mushoku Tensei got around to using this crap in its own novels (these arcs are from 2015 and on), plenty of other series had it as their central theme.

edit: Sugar Apple Fairytale is from 2010.