Message for my club members

Two people in particular have come to my Codes and Ciphers Club almost every week. One of them is always expecting a certain message to appear in the weekly puzzles, so of course I can't include it, unless I find a really clever way of disguising it so they won't be able to read it until they work out the rest of the puzzle. This is my attempt. This information is entirely irrelevant to solving the puzzle; it just makes sense of the solution.

I have included transcriptions below these images for your convenience. Note that the "cipher" tag, although it is the theme in my puzzles, is actually quite a small part of this puzzle.

Hints can be provided but I suspect it will be solved without them.

Credit: The image is taken from Seasons of Mystery: The Cherry Blossom Murders (video game)

-Left Column-
a.3-8-11/3-8-12
b.2-5-9/7-8
c.3-4-8/4-7-11
d.3-4-8/3-8-12
e.2-5-9/3-8-12
f.1-6-10/3-7-8
g.2-5-9/1-5-10
h.4-7-12/7-8
i.3-4-8/3-7-8
j.1-6-10/4-7-11
k.4-7-12/3-7-8
l.1-6-10/7-8
m.1-6-10/1-5-10
n.2-5-9/3-7-8
o.3-4-8/1-5-10
p.3-8-11/7-8
q.4-7-12/3-8-12
r.3-8-11/1-5-10
s.4-7-12/1-5-10
t.1-6-10/3-8-12
u.3-4-8/7-8
v.3-8-11/4-7-11
w.4-7-12/4-7-11
x.3-8-11/3-7-8
y.2-5-9/4-7-11
Joshua: UJXYSH
-Right Column-
H : VHKHKH
V : AWKRHKG
N : NYEATSKD
R : CEJFEK VJZ
W : AEAW
M : GHTVJSBEKW
O : XYBETA
Y : GYBWW
E : RBSTXGENDX
U : THAFW FWHM
D : YHGNYWG YHKRFW
F : WFD
T : NYWXX AEWNW
K : KWZXAHAWB
J : AENDHIW YWHR
A : NHG
P : AWKNEF
B : GWKKEX BHNDWG
X : YHGNYWG YWHR
G : NBJZK
S : GWRRL
C : XKHEF
Z : HNW JM REHTJKRX
I : GWKKEX VHFF
L : FHRLVSO
-Text along top of image (ignoring triangular symbols)-
CBVWHFIKTFSCFFEBAZZC


Hint:

If we treat the left column as a list of pairs of number sets, there is the same number of unique numbers sets as there are unique triangular symbols.

Right Column

By mapping each rune to a letter that it looks similar to it (like the "Joshua" example), we get the following list of items:
1. banana
2. pendant
3. chipmunk
4. violin bow
5. pipe
6. tambourine
7. shrimp
8. three
9. drumsticks
10. maple leaf
11. hatchet handle
12. elk
13. chess piece
14. newspaper
16. cat
17. pencil
18. tennis racket
20. crown
21. teddy
22. snail
23. ace of diamonds
24. tennis ball

Left Column:

From the added hint from @Joshua Bizley, there is a correlation between the number "codes" (ie. X-Y-Z) and the triangular symbols. 7-8 is the only code with only two digits, and the top-right triangular symbol is the only one with two small triangles, so they must go together. This means the second code in a pair corresponds to the horizontal symbols. The symbol to its left adds a small triangle, and 3-7-8 adds a number, so they match. Carrying on like this (I could add the full thought process here, but it was pretty straightforward) gives each triangular symbol a code, and the letter for each pair goes on the image at their intersection (shown in the image below).

Image

Circling each item in and adding each letter to the image gives us the following: