637: Always and Forever

637: Always and Forever is the second album by Japanese singer and actress Crystal Kay. It is her first R&B record; After the release of her debut album C.L.L Crystal Lover Light, Crystal started to move towards her new sound and made the transition with the single "Girl's Night". The album 637 features songs produced by well-known Japanese urban musicians Verbal, T-Kura, and Michico.

The album reached #19 on the weekly Oricon chart, and continued to rank for eight weeks. In all selling a total of 48,550 copies.