The overall design is amazing.
However, there are a few things you could improve.

Answers

1. Is it obvious that the word is supposed to be "Ayumu"?
   No. You should probably make the "AY" a bit closer to "U_MU" - as you said, it looks more like "AY U_MU" than "Ayumu".

2. Is it obvious that "U_MU" is supposed to be a face?
   Not at first glance, no - though the glasses are very obvious. It took me a minute or two to realize that the three letters were a face - but now that I've realized it, it looks a lot like one. It's best if you don't change anything to fix that - a few hidden gems is a good thing for all logos.

3. Is the green font too light against the white stroke?
   No - it is very easily readable. In fact, in my opinion, the color scheme is just perfect. The chinese letters are also very clear, though this is a question best answered by someone who actually knows Japanese - I don't.

4. Are the glasses' reflection too glaring for the eyes?
   No. Not at all - the reflection effect is perfect.

5. Is the overall logo balanced?
   Mostly. The structure of the logo is well thought out, and I love it - but the Chinese word is attracting too much attention, and "U_MU" is getting less attention compared to "AY", seperating "Ayumu" even more. So, I would suggest you switch the colours of the Chinese word and "U_MU" - make "U_MU" green and make the Chinese word grey.

6. Does the logo make you think of Japanese logos?
   DEFINITELY! With the cute style, the fun font, the bright stroke - saying it's perfect would be an understatement.

Extra suggestions

• Maybe remove the pink ellipses?
• Raise "AY" above the rim of the glasses.

Praise and Observations

I love the way that the part of the "_M" that intersects with the glasses looks a bit different.
When converted to grayscale, the logo keeps its clarity and Japanese cuteness, and still looks amazing.
The logo feels like it fits best for makeup-related things.