my childhood friend who i used to train swordsmanship with became a slave so i as an srank adventurer decided to buy her and protect her

a brief description of the manga 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: s-rank adventurer and second-generation sword saint, ryunoa styler, is reunited with his childhood friend, aine, who has been reduced to slavery. ryunoa purchases aine in order to save her, however, she’s been given a cursed collar that causes the wearer to go into ‘heat’ once a day… ryunoa’s battle to find a way to remove the collar starts now!