Way of the Fivefold Firefly Lantern
by Marc Saindon(Way of the Elements 5e variant)
I'm guessing that this 5e Monk subclass is to play Avatar: the Last Airbender in D&D. Which is fine, and can be played as is.
My spin on it: Sailor Moon.
This is can another "nocturnal" Monk subclass, with "night" not automatically signifying "evil". Think of your summer nights as a kid, trying to catch grasshoppers and grasp fireflies (something tablet kids won't know). Or, older, getting the gang together and drinking beer somenone stole from their parents around a campfire, watch the spark flies into the night sky, while roasting marshmallows or bacon on a stick. Night shouldn't get the 'evil' label.
So getting back to the Monk subclass, these guys are all about astrology (you can put a chinese twist on the Mystara zodiac signs), combining 12 signs with 5 elements (wood, water, fire, metal, earth) into a cycle that rules over fate. This means they are also a bit of math nerds and night owls. The typical Monk interprets himself as a star amidst a constellation in his meditations and star-gazing, so he'll likely pick a name associated with astronomy ("Rising Moon", "Setting Sun", "Sailor Patera", or the better name you'll come up with) and follow a path linked to that name and develop his elemental powers accordingly (Rising Moon might have a connection with Water because of the tides, while Setting Sun is more about fire).
There are many shrines spread throughout Ochalea (and beyond, as there are rumored "lost shrines" as plot hooks) that offers training in the powers of a specific element ("Casting Elemental spells" ability, although Air is NOT available as an element, although you do get Metal and Wood as new elements to learn from). A Water Shrine might be near the sea, on a icy mountain peak, at a waterfall or just be a wishing well; a Fire Shrine might be the forge of a legendary craftsman or a volcano; a Metal Shrine might be a mine or a scrapyard; etc. Monks from the Fivefold Firefly Lantern have a tradition of the "Long Pilgrimage", moving from shrine to shrine to learn from different masters (and creating adventuring opportunities for PCs). Older "lantern-bearers" might opt to settle down and take care of a shrine, while also becoming a mentor to visiting students. A shrine can also be challenged for in a singular combat.
Generalist "Fireflies" will various different shrines to learn various powers, while Specialist will prefer to stick to shrines linked to his prefered element. A group of traveling Lantern-Bearers might form a "constellation", for social and safety reasons, and might not all study all the same elements. A "constellation" might serve as a Power Ranger remake, with each member specializing in an element ("With our powers combined...").
In regards to martial arts, the Fivefold Firefly Lantern Tradition teaches Tai Chi, both the fighting style and relaxing method. They also do catch-and-release hunting of fireflies and craft neat paper lanterns.
Notes:
Chinese zodiac
Wuxing (Chinese philosophy)
Tai chi
(Image from: https://www.deviantart.com/shilozart/art/A-Sea-Of-Lights-with-Xiao-871359899)