Where do I drop...?

Help Summon Lightning (50567)
Help Summon Lightning This book teaches you the ability to strengthen Summon Lightning. [Click for details]	Found inside: Chest Help Books x1 Dropped by: Aku-Boku (Level 105) x10 ~30% HP 30,000,000 Strong against Trees Power of Earth Arboretum (Level 105) x10 ~30% HP 30,000,000 Strong against Trees Power of Earth Sycomore (Level 105) x10 ~30% HP 30,000,000 Strong against Trees Power of Earth