[I'm moralist (Yanagihara Mitsuki, iapoc)] Inmon Jakutai Joshishou ni Wakarase Ecchisuru Manga [MTL]

A busty, muscular swordswoman and her young disciple Yuto hunt goblins together—until the master falls to the monsters and her shota pupil decides it's his turn to protect her, awakening the lewd crest inked above her hairy crotch to make her understand her place. The proud warrior who always dominated her disciple ends up pinned beneath him, ahegao and teary-eyed, calling him a stupid disciple as he gives it to her just like Master always did. By the final page the hierarchy is thoroughly flipped: she struts in a revealing battle harness with her crotch tattoo glowing, flustered by her erotic disciple and daring him to prove he's more than just a man with a big dick.