Well... I suppose not every anime is Haibane Renmei.

The harem formula in Dual is the same as in Zero no Tsukaima: the chosen girl (the original Mitsuki) is fairly nasty, and an alternative exists which is far superior (Mitsuki II), but due to various circumstances the male lead is unwilling or unable to dump the chosen one. It's a serviceable setup, though ZnT extracted more mileage from it, being the ultimate harem etc.

They should have resolved it one way or the other.

Liked: It's ok. A comedy. Mindless.
Rewatch: No.