What software is good and complete useful for drawing anime?

I am a looking for a software that you can draw using a mouse example: many users are using Paint Tool Sai for drawing and sketching anime.

I am looking for that kind of software, full version and free with no payment.

I`ll show you what it looks like...

this is what paint tool sai looks like.. I am searching for a similar program like this one.. but more complete and useful. I got the same program and it said at the top of the bar 3 days trial, so I only downloaded the trial.

Can you guys help me and suggest a program?