deciphered text of the letter at https://oceanfalls.ams3.cdn.digitaloceanspaces.com/2019/12/00001219.png
(meant to be read down to up, left to right)

your day just as you always brighten mine.
may these feelings reach you, and brighten
thank you for everything you do.
your guidance brought us light again.
none other than you.
the protector of seas is a title fit for
you are a treasure made to be cherished.,
sea's children would have remained lost.
if not for that miracle, i am sure the
bringing about a miracle such as you.
every day, i thank the heavens for
dear kaji pyxis,

encoding scheme:
a - A
b - inverted B
c - left dot, inverted C
d - c wrapped in C
e - top left dot, inverted E
f - inverted F
g - top right dot, inverted G
h - H
i - deformed i/j
j - right dot/dash, inverted j
k - h>
l - inverted L
m - bottom right dot, M
n - combined nr
o - top dot, right dash/dot, 90 anticlockwise b
p - q
q (nonexistent)
r - inverted R
s - inverted S
t - upside down and inverted F
u - left dash/dot, U
v - right dot, V
w - top left dot, W
x - X
y - top right U, I
z (nonexistent)

notes:
- k consists of two runes - a 'h' and a '>'
- o/j, when to the left of u, turns the right dot of o/j and left dot of u into a combined dash
solved with the help of auto cipher solvers https://www.boxentriq.com/code-breaking/cryptogram