"Tsukiuta." Gekijouban: Rabbits Kingdom the Movie

A certain winter day. Hajime Mutsuki, the leader of the idol unit "Six Gravity," (a.k.a. Gravi) associated with Tsukino Talent Productions, aimlessly dropped by a secondhand bookstore and encountered Shun Shimotsuki, the leader of their sibling unit "Procellarum" (a.k.a. Procella).
The two of them picked up the antique classic which was thoug...