It is totally fine.

Yeah, it's his choice :)

Of course it is. Anyone should be able to wear anything they want, without judgement.

It's honestly a bit odd, but whatever. I personally would never do something like that though.

How would it affect my life in any way?

Depends on what you mean by "okay".
If you mean if a guy can wear a dress and not explode, yes, men can wear a dress okay and not get blown up due to the dress itself.
If you mean if a guy would look good in a dress....then it just depends on the man. Some men don't look good in a dress. I'd probably be one of those men that don't look good in a dress. Same goes for women, some women don't look good in a dress. Could just be an ugly dress. The men in the pictures looks alright, I guess.
If you mean culturally, most would say no.
If you mean by a man's choice, then that depends on the man. I don't think it'll be okay for me to wear a dress because I'd feel weird about it, regardless of what anybody thought. Nobody told me if I look good in a dress or not because I haven't worn one. If the man chooses to wear a dress and was okay with it, then it's just whatever, go ahead I guess.

Do what you want as long as it doesn't hurt anyboby.

I wear dresses all the time and so does one of my best friends.

lol go for it.
(I think all kpop fans are completely used to it by now xD)

^KPop more like JRock XD Ive seen it SO much more in JRock. I mean, every band has at least one XD

WOO HOO! GO HIZAKI!

^LOL BUT THIS!! link
This is the reason why people question it when I say that the blonde one is my favourite man on the planet xD

Abso-fucking-lutely
You wanna look fab? You look fab