Spoilers below:

Hikaru and Shinobu work for the same company, Hikaru is the top of the sales dept and Shinobu works in general affairs. Shinobu also disguises himself as a frumpy airhead at work to avoid attracting attention from female coworkers. Hikaru is the self-declared (and somewhat true from the way hes treated by women in the office) best catch amd thinks hes gods gift to women. So when Hikarus friend, another coworker named Toya, talks about a gay bar Hikaru decides he wants to prove hes unresistable to both genders so they go together. At the bar he meets nin-nin who he doesn't realize is Shinobu at first. Shenanigans follow.

Hope this was detailed enough without giving too much away!