Yuu, a novice healer gifted with the ability to mend monsters' hearts, is bestowed a peculiar bottle by his father. Upon contact, the bottle unleashes Merc, a liquid-formed girl devoid of her past recollections. Eager to unravel her identity, Merc and Yuu embark on a whimsical adventure across different lands. Thus commences the amusing and fantastical tale of Yuu, a healer-in-training terrified of monsters, and Merc, the enigmatic girl enclosed in a bottle.