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
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.