"ツ" aka "Tsu" was adopted as the official currency symbol of the project.
https://github.com/mimblewimble/grin-pm/blob/master/notes/20190117-meeting-governance.md#102-currency-symbol

“ツ” is very unique symbol.
It’s first time that Japanese katakana character is used in famous crypto currency project.
I need some months to accustomed with it because I'm Japanese. ツ