Kamiyain Fumi wa Bakuto ni Naritai!

Overview

Kamiyain Fumi is a fierce middle-schooler who gambles on mahjong parlors at night while being a member of the mahjong club by day... Or so she wants others to think! Fumi has never actually gambled, but acted like one to impress her friends in the mahjong club; that backfires when Tendou Hinata, one of the weakest girls in the mahjong club, tries to emulate Fumi by actually gambling. Now indebted, Hinata asks Fumi to play in her place to make up her losses. Fumi, unable to refuse, goes into the parlor at the time appointed by Hinata and discovers how frightening an actual gambling den is... Now, how will she keep her image and get out of there intact?

Source: AniList