Diablo/Relationships

Rimuru Tempest
Diablo is fanatically loyal to Rimuru.

Shion
They are rivals for being the "primary" secretary for Rimuru, though aside from that they both share a similar fanaticism for Rimuru, though for different reasons.

Black Numbers
Diablo's faction of subordinates, numbering several hundred. As a show of loyalty to Rimuru, Diablo returned to the underworld to recruit only the best of the demons to serve Rimuru. This included the Violet, White, and Yellow progenitors. They were named allowed with at least one lieutenant each. From this group, Diablo has Venom serving as his lieutenant.