Shunkashuutou Daikousha - Haru no Mai

From Yen Press: Locked in their endless dance, the seasons flourish but do not yield their time willingly to the winds of change. Transitioning them is a responsibility undertaken by humans known as Agents of the Four Seasons. Ten years ago, Lady Hinagiku failed in her duties as the Agent of Spring. Now, flanked by her loyal protector, Sakura, she has returned to thaw the cold winter once again. But the music did not cease in her absence, and for ten years, it fell upon the other Agents to uphold this eternal dance. If Lady Hinagiku is to fulfill her duty, she must bring spring to a world that has forgotten its warmth and find her footing among those who have carried on without her all these years.