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.

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. is a Manga/Manhwa/Manhua in (English/Raw) language, Adult series, english chapters have been translated and you can read them here. You are reading chapters on www.mgeko.com fastest updating comic site. The Summary is

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!