Faust is arrogant, but does not ignore others, and shows a gentle and kind appearance. She is a genius who developed the engine of Mephistopheles, the bus operated by Limbus Company. She knows about everything.

Yi sang is a particularly quiet, mellow man. He developed the "Glass Mirror", a device capable of reflecting the alternate worlds and timelines of the viewer.

They are Sinners(employees) of Limbus Company.

They are not afraid of death because Dante can always revive them.