The Japanese, and most Asian cultures that I am familiar with, are no different than westerners in this regard. Some conservative clowns say stupid crap like that. But that stop being the norm 50 years ago.  

Be friends?

If you were hungry and wanted to eat a sandwich... but the sandwich just wanted to hang out... would you sit there and hangout with it until you starve?

You could try to maintain the friendship if that doesn't work out you should just abandon the (friend)ship. More times than not friendships lose their dynamics though when one wants to take it a step further and the other person doesn't.

A sandwich can't express an opinion. I'd just eat the sandwich if I were hungry.

But in this scenario he likes the girl and the girl only wants to be friends. His options are to be friends or just ignore the girl. Better being friends and as tiem goes on her feelings might grow towards him.

whoa, simmer down champ. It's not misogynstic to say that if you want X and can't get X from the person then you go to someone else, that's a fact, if you tell yourself anything other than that you're dilluding yourself with no positive from doing so.

to close up your mind to the fact that one person wants 1 thing and the other wants something else, to continue the relationship in the hopes that either party will change what they want will just lead to bitterness down the road if either side does change their mind, if the guy changes his mind to the fact that he's alright that she has no interest in him as a partner then it's gonna mean sitting down to nice lunches with her to chat about the good dicking she got from some other guy and if the girl decides she'll give the guy a try with a relationship what happens then? There's gonna be a fairly bad conflict in him trying to be something he isn't to be what she wants from a guy (not him).

Honestly in your head think about it, if he is making posts like this about the girl and she gets herself a partner that isn't him, what are the chances that partner isn't going to tell Kapi to fuck off from hanging about her.

Lol you're saying that he has 2 options 1 is to walk away and find someone else, option 2 is to ignore her feelings and stay near her until she changes her mind.

What about the non big bang theory reality of the fact where she says she doesn't wanna date the guy, and then she doesn't ever date the guy because that was what she wants? I genuinely think that trying to stay hanging about as her friend in the hopes that she'll come around and give his dick a sniff to see what it's like isn't a healthy mindset, there's loads of guys around that she's prolly interested in and the OP could easily find a girl who is interested in him, the world is full of people. To lock into your mind for any lenght of time that "she's the one for me" while she's telling you directly to your face that she isn't, is wasted time.

Being friends with her is not ignoring her feelings since she wants to be friends. He can still find someone else while maintaining a friendship with his co worker. I just said that if he stays friends with her there is always a possibility that she could catch feelings too.

For that to happen / be of any use for OP then he would need to remain available on the chances that she changes her mind, unless he is going to get with someone in the mean time and then drop that person when this first girl decides to see what OP has to offer, but yeah in the mean time he is sat blasting rope to her facebook timeline holiday pics from 3 years ago! >.> I hear people do that... honest!

Move on,its going to be awkward now being with her,nothings gonna fix that

you should have though of this before,never go out with somebody at work or with common friends,cause if it goes bad as it has in your case,you should be ready to lose all your common friends cause its gonna be embarrassing you got rejected