Play as one of those police cars in the first stage.
To unlock this ship, finish the game on Easy mode without continuing or find 15 or more S. Bonuses.
This ship is very different from the Einhander and is recommended for more ADVANCED users of the game. Instead of gathering gunpods, it levels up and gains more power in its bullets just like a classic shoot-em-up game. If you die, however, you will have to start from its basic level 1. It max level is 20.
Without using continues, win at Hard difficulty. After the final credits, save the game and start a new one. At the Fighter Selection screen, cycle through the ships and find an Unknown Fighter Type II named the Selene. The Selene can carry 9,999 rounds of ammo for any weapon.