Synopsis: My childhood friend who I used to train swordsmanship with became a slave, so I, as an S-Rank adventurer decided to buy her and protect her.

Lunois Styler, an acclaimed S-rank adventurer famously referred to as the "second sword saint," comes across his childhood companion Aine, who has been captured and enslaved. In a bid to save her, Lunois acquires Aine, but soon discovers that she is compelled to undergo a distressing "heat" every day owing to a cursed collar. Determined to free Aine from her affliction, Lunois pledges to discover a means to remove the collar and bring an end to her agony.