Raikaken (jap. 雷花剣, thunder leaf sword) is an Iga dog Ninja attack which is used with multiple dogs. They hang upside down by holding onto tree braches with their hind legs then fall, attacking the enemy, often using leaves as a cover. The attack is used to cut or kick the enemy, then make a quick retreat back into the trees before they're noticed.

Characters that use this attack:

Akame (Ginga -Nagareboshi Gin-, Ginga Densetsu Weed)
Jinnai (Ginga -Nagareboshi Gin-)
Kirikaze (Ginga -Nagareboshi Gin-)
Tesshin (Ginga Densetsu Weed)
Toshimitsu (Ginga Densetsu Weed)