Bokomon

[On Play] Reveal the top 4 cards of your deck. Add 1 card with [Gammamon] in its text among them to the hand. Return the rest to the bottom of the deck. [All Turns] When one of your Digimon with [Gammamon] in its text, other than [Bokomon], would leave the battle area other than by one of your effects, by deleting this Digimon, prevent it from leaving.