This is my guess, coded message has 2 parts.
1st part: 1, 18, 9, 7, 1, 20, 15 is an alphabet cypher
replace the above numbers to alphabet you get A, R, I, G, A, T, O, which gives you "thanks" in japanese.
2nd part I'm unsure of: The seating chart was needed to indicate who
red is the...