Hi Ryo! The owner and other judge are sleeping right now (it's 2:50 am here in California). So, I'll give some feedback and then expect more in a few hours when they wake up.
The owner is looking for a graphic that incorporates a frog. She would like the frog to have personality, but not cartoonish. This means that body parts should be proportional, and it should not have too many human like qualities. However, she would really like to see a frog that connects with the target audience. For example (but please do not be limited by this), the pupils of the frog eye can connect with the audience. If you can make the frog show playful or curious traits, perhaps through its body position or integration with the text or some other part of the graphic.
The owner really, really likes circles, too. It appears she seems to be drawn to circular graphics.
Hope this helps. More feedback in about 5 hours.