Koi no Shinchoku, Ikaga deshou ka.

Salesman Hikaru Azuma and Designer Aoi Nayuki are like oil and water—their personalities clashing whenever they're in the same room. But when a boozy night throws them together in an unexpected way, things get even more complicated. Now, the two are forced to work side-by-side on a project, navigating their rocky past and the secret tangled between them.

(Source: Ichijinsha, translated)

Note: Includes an extra chapter.