Junpei, Ace Defective

When Junpei is dealt damage by a source you control, he gets a +1+1 counter

When Junpei destroys a creature exile the top X cards of your library where X is the excess damage dealt by Junpei, you may cast spells exiled this way until the next endstep

When you cast a spell from exile, deal 1 damage to any target human you control