One of the best ways to have a home party in a small space is having a home yakiniku party.
It doesn't take much. All you need is a ¥4,000 hot plate and a table. chairs optional as you get the best experience from eating while sitting on the floor. You can cook yakiniku outdoors if your balcony is large enough but if not then inside is fine too.
One big tip: make sure you have an open window and the kitchen fan on try and get the smell out of your apartment. You won't get it all but the unmistakable smell of yakiniku sticks in your clothes, curtains and anything else that can absorb a smell if left alone.
Second big tip: Do NOT have a yakiniku party if you have carpet. The oils from the meat while cooking spray everywhere without you noticing it. If you have flooring then prepare yourself with a mop and cleanser along with your Febreeze for the clean up after.
Once you are all set, invite as many friends over as can fit and be prepared to eat yourself into a stupor!