Generation Vii
Battle Bond
Defeating an opposing Pokémon strengthens the Pokémon’s bond with its Trainer, and it becomes Ash-Greninja. Water Shuriken gets more powerful.
Detailed Effect
Transforms this Pokémon into Ash-Greninja after fainting an opponent. Water Shuriken's power is 20 and always hits three times. This ability cannot be copied or replaced. This ability only takes effect for Greninja.
Pokémon With Battle Bond
2 canonical Pokémon forms can have this Ability.
Greninja Battle Bond 
Greninja Ash