Why is Ahagon embarrased with her name? And how does it match her appearance? Ahagon doesn't like her given name and introduced herself as Umiko. And Kou said her name matches her appearance.



Why is she embarrassed with her name? And how does it match her appearance? She pretty much always looks like this
While I had a feeling it was because it sounded like a kaijuu monster, I had no official confirmation until now. If you look at page 111 of the New Game! illustration book Fairies Story, it has an introduction of Umiko's setting, where it specifically states that 


  she has a complex about her name sounding like a kaijuu.


Note that Ahagon is a relatively rare name that comes from Okinawa. Most people would not be familiar with the name and if they've ever watched something like Ultraman as a kid, they might first think it's a kaijuu name, which is probably why it's become a complex for her.

Explanation about kaijuu
If you look at the list of kaijuu of the Ultraman series, you will see there are 98 monsters that end in "-gon". (Others include "-don", "-ton" "-mon" "-ron", and I believe it stems from how many dinosaurs end in "-don", so these endings give that same feeling of something large and powerful.)　It is a common game to add or change the end of a name to make it sound like a kaijuu. In English, I suppose it would like like adding "-(s)aurus" so the end of names to make them sound dinosaur-like".

As for "matching her appearance", I believe so because it she is Okinawan, and has a deep suntan. Okinawa is a tropical area of Japan, where it is warm most times of the year and with beautiful beaches, therefore it is full of heavily-tanned people. A bit stereotypical, but that's what a person would expect to see from an Okinawan.