Souten refers to azure blue skies as well as spring skies. While Youmu is sometimes called half-baked, she still aims to be a full-fledged swordswoman, and that refreshing energy of hers is reflected in this temperament. Youmu is endowed with Metal Phase, used in both swordsmanship and gardening, and Star Essence, as somebody who serves the ghost overseeing the Netherworld. The cold and silent Metal Phase resists Earth Phase, because earth bears metal, but it is weak to Fire Phase, because fire refines metal. The diverse and uncooperative Star Essence resists the cooperative and indecisive Moon Essence, but it is weak to the charming and arrogant Sun Essence.

While the ability may seem to simply explain Youmu's skill with the sword, it also shows her potential. Those around her tend to call her inexperienced, and her appearance does make her seem young, but if she were to go up against a regular human, she would be considered an expert with the sword. She follows the teachings of her fencing instructor and ancestor and trains daily (to the point that she eventually learns how to cut time itself). Her two swords also give her strength. Her long sword, the Roukanken, was forged by youkai, and her shorter sword, the Hakurouken, can sever lingering attachments and the cycle of rebirth. There isn't much that she can't cut.