From Kodansha:
To be reincarnated into another world with the promise of a "cheat" power is one thing but to be reborn as a baby, and then left for dead after your royal parents think you're powerless? That's another thing entirely. Now the newly-born Reinhardt or Haruto to his new friends must find his way through a dangerous world but luckily he's got magic that's quite literally off the charts.