In my experience, just unequip any HP enhancement, upgrade their attack power (and if you can, their armor), and DON'T DIE AT LEAST A TURN AFTER YOUR HP REACH <50% FOR BOTH OF THEM. Upgrade their tenacity with item or points helped too.
I can clear them with 0 item equip (or just equip items that boost attack/movement). Just be smart when attacking and moves through the maze.
This is an easier one rather than first Senhime quest, which is similar to this one, but SENHIME CAN'T BE HURTED by any means to complete the quest...