Yojimbo A collaborative new Fairfax restaurant is serving donburi and Japanese American fare from two veteran L.A. chefs. 426 N. Fairfax Ave., Los Angeles, 782-8331, toasttab.com/yojimbo Rumba Kitchen The team behind the Triple Threat food truck is opening a bricks-and-mortar Boricua restaurant in Little Tokyo. Rumba Kitchen, set to open Aug. 28 in Weller Court, will feature some of owners …