I saw there is a special socket to remove the cassette, but I don't own it. I was wondering, how do I remove it without the tool?

https://img42.imageshack.us/i/dscn6470.jpg/
https://img22.imageshack.us/i/dscn6471f.jpg/

That's not a cassette, that's a freewheel. Since it's just a 2-prong one you can pull the axle and try to use pretty much whatever(like a file) as a tool bit. But if you haven't got a freewheel puller you probably haven't got cone wrenches either, which puts you back at square one. freewheels are notorious for sometimes being fiendisly tight, so improvised tools are just asking for failure. Do it right, get the tool.

OR get the lbs to do it for you, it's a quickie.

I've attempted to remove a similar freewheel with a file clamped in a vice. The net result was a broken file. I would recomend taking the wheel to the lbs because it should cost about $5 and 5 minutes to remove the freewheel. If that's not an option, then purchase or borrow the correct tool for removal. If you absolutely can't do either of the above, I have removed similar freewheels with the very careful use of a hammer and punch in the slot to turn it counterclockwise.

The tool you need is pretty inexpensive (under $10.00) so if you're going to continue using this freewheel, It's worth buying. Otherwise you can let the LBS do it - they should charge $5.00 or less. BTW- freewheels are require a decent amount of torque to remove because they're tightened by chain tension, so are on as tight as when you stood on the pedals climbing a hill.

One consideration whether to purchase the tool, or not is what happens afterward. If you're reusing the same freewheel, or replacing it with a similar model, the tool will pay for itself. But if replacing it with a different brand freewheel, pass on the tool because it won't be usable next time, and consider buying the tool matching the new freewheel. (there are 7-8 different types)

If the freewheel is toast and you're replacing it anyway, you can use a drift punch to spin off the front plate and the freewheel will fall apart allowing you to clamp the body in a vice and turn it off. (the front plate spins off to the right)

+1

Suntour 2-prong freewheels can be difficult to remove at times, even with the correct tool. If you haven't done it a couple times with the correct tool, improvising tools is just asking for problems.