Rimuru’s sword is usually explained as being forged by Kurobe , but not as an ordinary plain blade. In the light novel discussion, it starts as a temporary sword made from pure magisteel , then later evolves after being kept in Rimuru’s body, eventually becoming Hihiirokane before Kurobe refines it again into a proper sword.

What likely caused the confusion

  • Kurobe did give Rimuru a temporary normal sword at first, because the stronger one was still being prepared.
  • That blade was later upgraded rather than replaced immediately.
  • Some fan discussions describe it as black in its base state and only showing special colors when Rimuru infuses it with aura or magicule.

Simple answer

So the “divine steel” idea is probably a mix-up with later upgrades, fan wording, or the sword’s transformed state. The actual blade Rimuru used was originally a Kurobe-forged sword , not a separate divine-steel weapon handed over at the start.

TL;DR

Rimuru got the sword from Kurobe , first as a temporary magisteel blade, and it later evolved into a much stronger weapon.