All you have to do is look at the profiles and charges for other teachers with your English teaching qualifications.  You will see some with great feedback who have taught many lessons. What do they charge? Over time the closer your profile gets to theirs, the more likely it is that students will be willing to pay that rate. Your charges could increase over time as your profile strengthens. A novice would really need to have excellent teaching qualifications to consider charging above average rates without a good lesson and feedback history

The problem is that your prices are very high compared to those of other Japanese community tutors on this platform. Some professional Japanese teachers charge roughly the same as you, but most charge less. On this platform, $25/hr is a premium price (at least for Japanese). So, students willing to pay that sort of money have lots and lots of teachers to choose from, and they're more likely to choose a professional teacher with a lot of experience and a lot of positive feedback. 

Maurice has written pretty much what I wanted to say. :) Look around, do the research and see what price is appropriate to ask for your teaching level.

I recommend against setting a very low price, just to "attract students". Students here will pay for quality, and a low price might make your lessons seem low-quality. Also, decide for yourself at what point a price isn't worth your time. Keep in mind the commissions taken by italki and your payment system (eg. Paypal) so you know what you'll really get per lesson.

One more thing: stay patient. Some new teachers get students immediately, while others have to wait for a few weeks for their first student. Don't doubt yourself if students aren't rushing to book lessons. Just build it up gradually and surely.

Welcome to italki teaching, and good luck!