I want to remove part of a string (shown in bold) below, this is stored in the string oldString
[DMSM-8433] 加護亜依 Kago Ai – 加護亜依 vs. FRIDAY<
I think you should use a regular expression like this one:
([\p{Hiragana}\p{Katakana}\p{Han}]+)
please refer also to this documentation.
EDIT: I also tested it here.