Konosuba: An Explosion on This Wonderful World!, Vol. 3 (light novel): The Strongest Duo!'s Turn — Natsume Akatsuki

A GREAT ADVENTURE STARTS OFF WITH A BANG!...AND A WHIMPER.
Axel-a town where many would-be legends find their humble beginnings. It is here that the Crimson Magic duo endeavor to leave their mark on the world...but the only kind of mark Megumin can leave is a giant, smoking crater. And most parties simply don't have room for a wizard limited to one excessively powerful Explosion per day. Sadly, Yunyun isn't doing any better. Every party-request flyer she posts reeks of desperation, and her self-confidence bar is in the red! Will no one take a chance on these poor problem children?!