Horn

Horn is a supporting character introduced in How NOT to Summon a Demon Lord (particularly prominent in season 2 / Omega).

She is a young Grasswalker (a rabbit-like demi-human race that appears childlike, despite being around 12 years old in appearance). Horn is an adventurer from Zircon Tower City who specializes in thief/seeker skills, such as lock-picking, dungeon guiding, and stealth abilities.

She joins Diablo's party as a temporary/part-time member and guide after meeting them in the Zircon Tower area. Horn has an outgoing, friendly, and sociable personality, though she's innocent in some matters and can be shy (e.g., about certain clothing like mini skirts). She later takes a break from the group to study magic.

(Note: As a Grasswalker, she has animal ears and a tail, and her design fits the series' typical fantasy aesthetic.)