There are some more ancient religions that posit the natural world proceeds from one of the divine; that an unseen ordinance governs and guards the flowing of a stream, or the changing seasons.
Despite mankind's many scientific breakthroughs attributing all observable phenomenon to a reasonable and sound calculus, there are some obscure corners of existence where the influence of spirits holds true.
Benevolent spirits who preside over their domains subsist off prayers of their faithful; wrathful spirits can perhaps be placated with offerings or praise. Thus this is the duty of a shrine maiden — to commit oneself wholly to the service of the divine.
Without question, hesitance, or doubt. None were more committed, his master would note, than young Yukio. Orphaned at a young age, Yukio spent most of his formative years as an acolyte.
Under the tutelage of his master, a wise and venerated sage, he would learn all the necessary routines and responsibilities for his service. Yukio loved his teacher like a father, however tragedy would soon strike as their whole region became gripped by a dreadful winter.
Wracked by his already failing health Yukio's master would pass away one night, leaving the care of his beloved shrine to his pupil. After burying his master and providing proper rites, Yukio became overwhelmed by a depressive grief. Likewise the winter worsened, eventually becoming so deadly the nearby village was promptly evacuated.
Despite an urging from the villagers to abandon his shrine, Yukio refused and vowed to remain despite the cold encroaching more-and-more with each passing day. As firewood and food supply dwindled, the young maiden remained steadfast despite the dire desperation of his situation.
Then one day as he lay there, curled and huddled upon the polished wooden boards of the shrine's innermost sanctum, he suddenly couldn't feel the cold! In fact...he couldn't feel much of anything. Had Spring finally returned? Surely it must have! Believing himself to be saved, Yukio ran to slide open the door!
Only to notice his hands passing right through the smooth paper surface and slim wooden frames. Nonplussed at first, he'd just float there gawking at the empty space in front of hi--...wait! Floating!? He looks down at his legs, feet hovering inches off the ground.
Panic sets in before without thinking, he moves forwards through the doorway, phasing to the other side. No...no! No no NO! Is he dead!? He is! What's worse is he failed to pass through onto the other-side! He's become a ghost, a shade, a maiden eternally snowbound.
A literal snowman. Lamenting his loss of body Yukio would float up to top of the hill, the place where he'd buried his master. He expresses his frustrations aloud to the headstone, how he wishes only to feel the warmth of his master's embrace once again. However, truthfully Yukio knows they'll never be together again.
His master was gone now, a decaying heap rotting in the earth below. Becoming one with the soil, the sky, and the snow. As the mournful maiden levitated there, too distraught to muster energy to cry, he'd notice a familiar glint. Over the jagged horizon the first sunlight of Spring would wink, filtering into view with a warm wind washing over the hill!
Just at Yukio's feet the snow is blown away, the meager green of life starting anew apparent beneath him. For an instant he could've sworn he felt someone's arms wrapping around his shoulders from behind, but when he turned to look they were gone. The joy swells up in him so, that it escapes as thick, bulbous tears rolling down his boyish cheeks.
As his tears grow into a shallow stream flowing down the hill, many stick to his soul like glue. They condense, packing in tighter...and tighter until he feels himself being swallowed up! Yukio's entrapped within paltry meat once again, albeit tinged blue as his body comprises mostly water.
He felt over himself, shifting his feet against the grass to take in the sensation of touch, the sensation of his weight succumbing to gravity. As the seasons came and went, Yukio put his body to good use tending the temple. However he was perplexed as to why none of the villagers were returning, as the months turned to years and years into decades.
Many travelers and strangers would come through, sometimes spotting Yukio but never stopping to chat. It was rare the little yokai would receive a visitor. Eventually the rumor became that the whole village was haunted, with particular activity being centered on the shrine's grounds.
While the whole town fell into dilapidated disrepair, the passage of time seemed ineffective against the temple. So it goes, even to this day the spirits preside over far corners of the world; so too do the shrine maidens who wait on them. Rest assure though, none are more committed than Yukio.
Just some vague ideas I put together for either long-term or one off scenes. Don't feel the need to use them or anything, and don't be afraid to add your own suggestions in either!
1.) One morning while Yukio is making his rounds and tending the shrine, he comes across another more powerful spirit who's decided to take residence there!
Perhaps they were injured in combat and sought a safe place to recover? Maybe they're forlorn and merely seeking refuge or shelter? Whatever the case, Yukio will wait on them upon his hands and knees.
If not out of the kindness of his heart, then out of fear for his own safety should he scorn them.
2.) A priest/exorcist is called in to handle a purportedly 'dangerous haunting' in a long abandoned temple.
Through some harmless misunderstanding, poor Yukio's been pegged as a malevolent specter out to torment mortals. Maybe if he gets the chance to explain himself, things can proceed peacefully. Then again, perhaps they'll see to a more direct method of vanquishing the yokai instead.
3.) Haunting the same shrine for a few centuries could turn anyone restless. With his sense of duty overcome by his curiosity, Yukio goes abroad to strange new lands beyond his snowy mountain home. Of course, it's never a good idea to travel unaccompanied!
Hopefully he'll meet some charitable fellow traveler to guide him, or a friendly local to take the strange lad in and keep him out of trouble for awhile. However, it's also quite possible he'll just fall victim to more unsavory and shady sorts.