Hi Naoki. I used to be an online English tutor here in the Philippines. I have to say that just every other jobs out there, it has its own pros and cons. One thing I liked about my online English tutor days was having to experience the comfort of working from home. You don't need to allot any allowance for your taxi or jeepney fair and I can choose my own time to get to work and stop whenever I wanted.
About the cons, there are times when I get bored and miss having to go on lunch with my coworkers and catch on office events. You also have to pay your own SSS, PAG-IBIG and PhilHealth contribution as the company won't do it for you.
Of all the ESL teaching companies I have worked for, I recommend BiBO the most. Training is easy and you can get hired in just one day.