"Who am I..."
O divine spirit awakened in the depths of the sea, you bear three seals from Takamagahara.
You are a tsukumogami of the blade, the foremost warrior of the age of the gods.
In those distant eras, you were the sun that illuminated the world,
the moon that brought peace to all things...
Your existence made the world more brilliant.
Your passing left it shrouded in darkness.
You were the world's darling, yet this world
made you spend everything you had...
My beloved divine spirit...
"You are... Juroya Munetika."
P.S. The love interest is undecided, maybe the older brother.
There are alternate endings set in Heian-kyo, the Warring States period, and the Shinsengumi era.
A little angst is good for the soul, but too much hurts, so the author has chosen to hurt you.
None of the three eras has a happy ending. Take care, and proceed with caution.
Theme: Don't wait until you've lost something to regret it.