Sword Saint Adel's Second Chance: Volume 2

Upon returning to the past, Swordmaster Adel became turned into woman and gained the powers of a Saint. Now known to all as Saint Adel, she dedicates herself to training to master her newfound abilities to better protect her beloved liege, Princess Euphinia. One day, the royal court receives news that the northernmost Holy Tower in the kingdom has broken down, reverting the surrounding territory into an area filled with miasma and monsters. Hurrying to the site to handle the crisis, Adel encounters a force already in battle against the monsters, led by none other than Mad Emperor Tristan, who was deeply involved in the plot that took Euphinia’s life in the previous timeline! Her immediate impulse is to leave him to his demise, but strangely, he now seems nothing like the cruel and calculating man Adel once knew... Uncertain who is friend or foe, Adel once again summons her newfound powers and steadfast allies to fend off the darkness lurking in the kingdom’s shadows!

[From J-Novel Club]