Natalie

Natalie Jr. is a new guild receptionist at the Adventurer's Guild in Flatta village. She shares a name with her predecessor Natalie.

Natalie Jr. is the one who reveals that Azusa has achieved max level by killing nothing but slimes for over 300 years with her Increased EXP Acquisition ability. However, due to Azusa wanting to keep a low profile and continue with her quiet slow life, she requests that Natalie keep her stats and level a secret, to which, Natalie agrees.

(Source: Slime Taoshite 300 Nen Fandom Wiki)