YSS Ryoku, NG-S4-504, is a Plumeria-class (2D) Medium Gunship built at Legacy Bastion (Katsuko no Iori) by Ketsurui Fleet Yards in YE 33 for the Star Army of Yamatai's Fourth Fleet. She was built as a 1D variant. She is commanded by Taisa Shao. The Ryoku is painted with a squadron leader color scheme chosen by her commander.

Ryoku means strength in Yamataian.