Invadion is a defense RPG game set in a world on the brink of extinction due to a massive invasion. Your mission is to protect humanity by defeating the flood and upgrading your weapons. The game offers a unique twist where you can win items to defend the city and increase favorability with attractive beauty girls.

In Invadion, players can try out various bullets with different attack powers based on their grades. From Normal to Legend bullets, each with its own reset limits and required items, offering a range of attack powers. The game features 15 regular stages, 15 hard stages, and 4 special stages for an engaging gameplay experience.