TWilight INSanity is a pretty decent doujin shooter by Eikyuu Loop, also responsible for the development of Iincho and Clover Wing. You can swap characters by pressing the X key, though the second team is perhaps the strongest out of the three.

Press the control key to skip cutscenes, and use the space or C key to vary your movement speed. Tap the Z key to initiate the special tension attack.

Name: TWilight INSanity
Developer: Eikyuu Loop
Category: Shooter
Type: Freeware
Size: 60MB