Hammsuke's Classmate, Mechanical Pencil Hammy

:[Choose a normal unit with "Hammsuke" in its card name from your drop zone, and put it on the bottom of your deck] When this unit attacks a vanguard, you may pay the cost. If you do, choose one of your other rear-guards with "Hammsuke" in its card name, that unit and this unit get +4000 until end of turn, and at the end of that turn, retire the unit chosen with this effect.