What is the proper way to measure? I don't consider myself big, but at fuzoku get the comment "ookii" sometimes. Do girls say this to everyone? BTW, I'm Asian American of small stature and build.
You measure from the top and from base to tip. Average is 5 in to 6 in (12.6 cm to 15.25 cm).
Above 15 centimeters is unusual in Northeast and Southeast Asia, which is where a lot of the surprise comes from. The further above 15 cm, the more shock.
Another point is many women in Japan are not used to deep penetration or may have never been deeply penetrated. It evidently takes various women a couple times to get used to or it's better if they had deep penetration in the past.
From experience, it may take a woman 2x or 3x on separate days to get used to. Particularly younger Japanese women. Possibly, there is adapative changes in the vagina. Women who are used to deep penetration, having her cervix touched by the penis, or cumming from deep penetration can develop a preference for longer penis. This can be why shorter penis men do preemptive attacks to attempt to have women be fearful of longer penis men. In Japan, this fear pushing is very very obvious
Also, for the first time, it's not so much that a longer penis hurts, but that she never felt the sensation. The mindset and how she interprets the feeling is very important.
Japanese women in particular, due to the constantly pushed propaganda and mantra that large penises hurt, can interpret deep penetration as pain. Their mind has been conditioned to think that way, where in contrast, women of other countries can WANT to feel deep penetration or are positively curious to know how it feels.
It's particularly weird, from my experience, to see this oddness with tall Japanese women. Many taller Japanese women can be trying to prove desparately hard that their vagina is extra small. So you can have short Japanese women that can easily handle large penises, while tall ( above 171cm) Japanese women act like they will die from penis bigger than 15 cm, which is highly illogical.
Many Japanese women will act surprised or say a larger penis hurts, in an often FAKE act to show their vagina is extra small or they are virgin-like. This can be a conscious attempt or at times something unconscious that got pushed into their mind. This is a type of child-ish mindset where various women think acting like they are bad at sex or acting like a teenager is a turn on to all men (many don't know how to adapt to different men with different thinking). I have been to many countries in Asia, and the size issue is particularly distinct in Japan more than other places.