Although there are already quite a number of writeups for this task, I realized my approach was different as most writeups make use of the knowledge that the starting 6 characters of the message is TWCTF{

My approach only cares about the pipe character in the middle of the message. I suppose in a way a more flexible approach.

Original writeup (https://dowsll.github.io/writeups/tokyowesternctf2017/mysimplecipher).