Protect the Sign! Attack of the Dojo Challengers! (守れ看板!道場破り襲来!) is the 17th episode of the History Strongest Disciple Kenichi series. It first aired on February 3, 2007.
Rivals from another dojo break into Ryōzanpaku to challenge their masters, but with only Kenichi and Miu present, the two must confront the rivals alone.