The poem pictures a young woman who has died, and it sets her youth against the age of her remains. She is "as bright as gold" and has a "soul so young," yet her body is "a corpse so old." That clash is the heart of it: she seems frozen between being a girl and being long gone.
The speaker sounds more like a quiet observer than someone in grief. The tone is gentle and almost reverent. The body is called a "delicate casket" holding "dry and hollow bones," which makes her feel fragile and emptied out, but not frightening. The "seasons past" suggest a lot of time has gone by, and the sakura leaves covering her "like a mist" soften the scene. Cherry blossoms are often tied to beauty that doesn't last, so they fit here.
The mood is wistful, still, and a little haunting. Death looks sad but also strangely beautiful, as if the falling leaves are tenderly hiding what time has left behind.