Mystery Y: Lightning Style - Kirin Y: Launches a Barrier for 3 rounds, increase Attack and Ninjutsu by 40% for the Lightning attribute units in your Lineup. When using this barrier, this mystery gains and causes Lightning attribute damage to 4 units on the Opponent’s team and will cause a selected unit to suffer from Knockdown. The barrier does not disappear

This is probably the skillbook that was somehow incorporated with one of the kirin books.