Karous (カラス, karasu, "raven") is a video game by Milestone Inc. intended for the Sega NAOMI. The game is a vertical scrolling shooter, similar in this fashion to Radilgy. A Dreamcast version was released in March 2007. It's the last official game released for the Dreamcast in Japan.
The weapon system is based on Radio Allergy, but it uses a unique D.F.S. bomb system.
Bombs can be used when SP gauge is full. When a bomb is activated, a barrier surrounds the player, which can damage enemies within the barrier. For the duration of bomb activation, the player is invulnerable. Enemies destroyed by the barrier provide more experience points to the player.
The player's shot, sword, shield can be upgraded by using experience items dropped from enemies, with a maximum of 100 levels. Weapon levels also act as score multipliers.
Source: Wikipedia, "Karous", available under the CC-BY-SA License.